how do I replace drive belt for murray 40507x8c?

Before strting this a manual or diagram would help you. I found this in less than a minute http://www.partsandservice.com/html/Murray/lt/lt40507x8c.html I will reseach and get back to you with more info but you can surf some too.

This gives you an idea of how it goes , not sure what all you have to take off.
Most of the time you have to remove the front pulley,
Unless you can get it by the belt guides.
Luck

Good timing B whe have ti stop meeting like this