I have a john deer riding lawn mower, model 115. I have never had any problems with it until today. I started the lawn mower and it was as if the throttle was hung wide open. I don't have a clue as to how to fix it and I know not to run it running this high. Can anyone help?:)

It may be a Governor spring is off the carb or the linkage is hung up there. This would make it run flat out id it isn't possibly the cable itself.
One other thing is a carb gasket could allow too much air into the carb throttle body and that can cause it to run wide open. A carb acts like that right before you run out of gas because its more air then gas going to carb.

One test for the carb gasket is to partially put your hand over the carb bowl and if that doesn't choke it out some then its getting air from somewhere else ( bad gasket )