First post here - hope to be helpful.
Using the info previously shown, I just swapped both serp belts on the wife's RX. I'll break it up into two parts, as you may just want to do the AC/Alternator (outer) belt.
Part 1 - the AC/Alternator (outer) belt:
1/4" drive 12mm socket
3/8" drive 12mm socket
3/8" to 1/4" drive adapter
3/8" drive ratchet
3/8" drive 14mm socket (a 9/16ths is close enough if you don't have one)
1/4" drive 10mm socket - needed for doing the second belt anyway)
1/4" drive bit-driver (like a screwdriver with a 1/4" drive adapter on the end)
1/2" drive breaker bar - needed for the second belt
1/2" drive 14mm socket (again, a 9/16ths with six-points is close enough)
Small Flat-head screwdriver
One Zip Tie
Optional: First, I removed the coolant cap and placed it on the engine cover to get the coolant hose out of the way. I then used the small flat head screwdriver to release the clip that holds the electrical bundle off the alternator, so I could zip-tie those wires out of the way. I'll say this is optional, but it will make your life 100x easier to have them out of the way.
Second, break loose bolt A in the picture below. It's the 14mm, and I had to use a breaker on mine with a 6 point 9/16ths. This is fine, just be careful that the socket is all the way on the bolt, and that you don't round it off.
You will then need to loosen bolt B, a 12mm. I used my 3/8" ratchet, 3/8" to 1/4" adapter, and the 1/4" drive 12mm socket. Without the little gap from the adapter the alternator pulley gets in the way. This is a slow process as you really only have thirty degrees or so to play with of rotation, but get it nice and loose (finger loose).
Then use the 3/8" drive 12mm socket and the 3/8" ratchet to loosen bolt C. This bolt will be the bane of your existence. No space to work, and slow moving. Once you get it somewhat loose, you can use one hand to pull up on the alternator to release any tension on the bolt, and use your other hand to thread it out quickly. Still wasn't that easy, as I had to wear gloves because the engine was hot.
Note - you can see bundle D - that's the electrical bundle off the alternator zip tied out of the way.
In the lower diagram below, I have the Pivot Bolt marked as A, Adjusting Lock Bolt as B, and Adjusting Bolt as C:
Second view with same notes:
The optional 10mm may come in handy to remove the bolts holding the front bumper undertray (panel between the bumper and the engine undertray - bolts toward the back of the car). I dropped the 12mm socket twice loosening B, and once the whole ratchet loosening C. Removing the 10mm's (four of them) will allow you enough clearance to pull it off the body and shake out whatever you drop.
Once it's good and loose, remove the belt. I went on to do Part 2 - replacing the Power Steering (inner) belt.
If you're just doing the outer belt replace the belt, swear some as it's a PITA to get over all the pulleys, and tighten using Bolt C. (Routing is easy - no rollers to worry about, just get it around all three pulleys.) Once it's as tight as you want (I had to exert some force to get 90* twist in the middle), lock down Bolts A and B. Clip the zip-tie on bundle D, put the bundle back in the factory clip on the front of the car, and replace the coolant cap. You're all set.
Part 2 - the Power Steering (PS - inner) belt:
3/8" drive 12mm socket (should have from Part 1)
3/8" drive ratchet (from part 1)
1/4" drive 10mm socket (may have from part 1)
1/4" drive ratchet or adapter for 3/8" ratchet (which you would have from Part 1)
1/2" drive 21mm socket
1/2" drive breaker bar or ratchet (may have from part 1)
Long (12") flathead screw driver
1/2" drive 12mm socket
3/8" drive short (1") ratchet extension
At this point my helper had to go inside - don't want him messing around when the car is on a jack/jackstands.
Use the 21mm socket and 1/2" drive ratchet or breaker bar to loosen the lugs on the front right wheel. Just a couple threads.
Jack up the front right corner of the car and place it on a jackstand. I put the jack in from the front, and placed the jack stand behind it along the frame - kinda behind the susp/brakes.
Remove the wheel and place it out of the way. I as a practice always place the wheel under the side of the car, and lower onto the jackstand, then place pressure back on the jack. This way the jack and jackstand are holding the car, and if it slips the wheel will break some of the fall. (More important in little sports cars, the height of the RX means it likely wouldn't hit the wheel anyhow.) You may sacrifice a wheel if it falls on it, but better the wheel than your face (assuming you are working under the car).
There you can see the jackstand behind the brake area, along the frame.
Now use the 10mm to remove the two E bolts shown below (inside the passenger wheel well, towards the front of the car).
I neglected to take a picture before I removed the inner belt, but you will have to loosen bolt F below, a 12mm. Mine was super tight, so I used my 1/2" drive 12mm and breaker bar.
Bolt F can then be loosened pretty easily with the 12mm. I used the 3/8" drive ratchet and short extension with the 3/8" drive 12mm socket to loosen it quite a bit (without the extension it didn't have clearance, and using the breaker bar with the 1/2" drive socket would take forever).
Once F is good and loose, I squeezed both sides of the belt to move the PS pump up and release tension on it (making gap G smaller). Remove the belt, replace with the new one. (PITA just like the belt for part 1, but eventually it goes on.)
To tighten the belt, I put a long flathead screwdriver in gap G and pried downwards toward bolt F. Once I liked how tight it was, I tightened bolt F up and was ready to go.
I did not make the inner belt as tight as the outer. A.) it would have been a pain to pry that hard. B.) as previously noted the PS pump rotates pretty easily and likely doesn't need to be that tight.
Since I was doing 1 and 2, I waited to replace the cover panel ant bolts E until after I got the outer belt on from part 1.
Put the panel back in place, replace the E bolts. Put the wheel back on, remove it from the jack/ jackstands. Finish up the Part 1 ending, and you're set.