OK
If you are trying to turn a dollar then search the web for the MTD "Must have manual of outdoor power Equipment"
There are 4 volumes and ride ons are covered in volume 2 "Rear Engine Riders & Lawn Tractors
Vol 1,2 & 4 can be found
at K & T's web page plus a lot of IPL's and their parts prices are reasonable
Usually with a vari drive system, you start by setting the parking brake
Next is flipping the belt off the rear tensioning pulley # 64
The remove the large drive pulley # 62 as most use the rear frame as belt keepers
Then the top belt usually can be slipped off
Following that you slip the front belt off the variable pulley
Then undo / loosen the 2 clutch pulleys so they will drop far enough to get the belt off them
Last bit is to undo the engine pulley and slide it down as most MTD's use tangs in the frame as keepers for the front belt
Replacing is as they say the reverse of removing
On some the variable pulley mounting has to be loosened so it moves a bit ( not needed to be removed ) as again it runs near the frame to use the frame as a belt keeper