To solve for variable m, bring all the numbers on one side, say right side. For that add 8 on left side which will cancel out 8 on left. When you add or subtract anything on left, you add or substraction same on right side. So add 8 on right side.
2m + m —8 = 7
+ 8 =+8
3m. = 15, Next divide by 3 on each side
3m/3. = 15/3
m. = 5