Respuesta :
take away m from both sides to get 15=2m-9 and add 9 to get 24=2m, next divide by 2 to get m=12
move the first m to the right-> 15=3m-m-9
15=2m-9
add 9 to both sides-> 15+9=2m-9+9
24=2m+0
now divide 24/2
m=12