Here is your equation:

You're looking for m. To find m, you have to remove everything on the same side of it. On that side, you have:

You have
. To remove it, you have to do the opposite of it, which is
. To leave m alone, add
to both sides.

You have your answer, which is 
<em>If you have any questions, feel free to ask in the comments! :)</em>