You have to add 10 to both sides of the equation because you want to have your variable (in this case it's K) to be on it's own. K=-7+10 or K=10-7 Then you subtract 7 from 10 and you get k=3. Let me know if you don't understand.
m is 48 because since they said perimeter you would have to add 3 twice and then subtract is with 102 which is 96 the divide 96 by 2 and you would get 48.
