Combining like terms means, in this case, add the m's together, and get the numbers without variables together, so
if you add 5 to the -5 on the left side of the equation, you can get rid of it there, but must now add it to the opposite side of the equation, giving you 38 on the right side of the equation. 3 must be subtracted from both sides as well, giving you 35.
You now have
from here, the variable, in this case m, needs to stand alone. To get the m alone, you must now divide 7m by 7, as well as 35 by 7 (always remember, what you do to one side, must be done to the other), therefore, m=35/7, or m=5.
Hope this helped! Good luck!