Answer:
m=7
Explanation:
When solving this expression, you need to do the opposite operation. But first you need to get the m by itself. So you divide by 3 on both sides. 3/3 is 1 so you get left with m=21 at that point. Then you have to do the same thing to the 21. So you divide 21/3 and get 7. Your final answer is m=7