It takes even 63/4 hours to mow 3 lawns it takes him 21/3 hours to mow mr gals lawn and 13/4 to mow mr lees lawn.

Ok so Mr gals takes 7 hours and Mr Lee's takes 6.25 hours to mow and those added equal 13.25 so 63 divided by 4 equals 15.75 so if we take that and minus gal and Lee's lawn it takes 2.50 hours to mow Mr unknowns lawn