I need to repair the clutch/brake on my sears craftsman 19.5 horse power riding mower. I have no stopping .

This Is A Simple Repair, Lay Down Behind The Rear Wheels Of The Tractor With Your Head To The Right Hand Side Of The Unit. Look Up And Forward Just In Front Of The Axle And You Will See A Disc, Or A Small "s" Shaped Bracket With More Than Likely A 1/2" Nut , Take The Wrench And Tighten This Nut A Little. Try It And Then Tighten More To Make The Final Adjustment.

I have a 1999 mtd lawn mower and the brakes don't work good

Try the same adjustment,or replace the pads behind the adjusting nuts.

I just bought a craftsman lawn tractor model # 917.28856. Used it 5 times and tried to get it out when parking brake will not release. Suggestions?

As sitting on yard tractor- the right rear, just in front of your rear tractor axle - you will see a round disk (rotor) generally in the bracket you will see a center nut approx.1/2 in. place shifter in neutral- turn wheels - if wheels no turn - make sure you are not in park- turn wheels- if still no turn- loosen center 1/2 in. nut (but do not remove) still no turn- tap with rubber mallet or orange plastic dead blow hammer ( to release) tighten nut clockwise slowly while turning wheels- when you feel a slight drag while turning wheels-stop- turn counter clockwise 1/4 turn then stop- you should be good. Sometimes if they sit for awhile they won't release. I jack the rear up and remove the right rear wheel for easier access. Good luck! Be safe and make sure tractor is stable by supporting with jack stands.