-(m-8)= -8m+29
-1(m-8)=-8m+29-------------Note: there is always an invisible 1 in front
-m+8=-8m+29---------------Subtract both sides by -8
-m=-8m+21-------------------Add both sides by +m
0=-7m+21---------------------Add +7m to both sides
7m=21 -------------------------Divide both sides by 7
m=3