Most Murray riding mowers are held on with either a C-clip or a snap ring.
Remove the hub cap by prying if off with a screwdriver of small crow bar.
The look to see if you cahve an open ended c-clip (Some call it an e-ring)
If id does, then take a screwdriver and put it into the e-ring and pry it off.
If it is a Snap-ring, you will have to get a pair of snap ring pliers. Put the end of the snap ring pliers into the two little holes of the snap ring and squeeze the pliers to open the snap fing. Then pull of the snap ring. You the MIGHT be able to pull the tire and rim off....
I said Might because many times the wheel rusts onto the shaft and won't come off. If this is the case, you should get some penetrating oil and spray on BOTH sides of the wheel on the axle. Do this every hour of about 4 hours. then pry to remove it again. IF this does not work, comtinues spraying the oil a couple more times and then waid until the next day to do anything else.
You can then...after you have waited 24 hrs for the oil to work, take a hammer and "GENTLY" and I MEAN "GENTLY" Try to tap the wheel on the back side to try to remove it. DO NOT TAKE A BIG SLEDGE HAMMER AND PUND THE HECK OUT OF IT!!!!! If you do , wyou will greak the snap ring inside the transmission that holds the axle to the gears and the axle will come out in your hands makeing it so you have to rebuild the transmisstion....$500.00
If it doesn't come out with this gentle tapping, you can then try taking a Punch almost the size of the axle and hold it against the axle of the transmission while having someone else put some pressure on the wheel and they you can hot the top of the puch and try to jaar it loose.
DO not over-do this as you will flare the axles and make it impossible to get the wheel off. do not heat the wheel or axle with a troch as you will ruin the seals in the transmission.
If this doesn't work, then it is time to take it to a professional..
You don't want to cost yourself a $500 or more repair job.