First distribute the (-) in front of the quantity of 3 - 4m. Think of it as this:
-1(3 - 4m)
You multiply each number inside the parenthesis by -1.
So:
3*-1 = -3 -4m * -1 = 4m
Now that you've distributed the negative you can remove the parenthesis. Now you'll just set it all up like you would any normal problem. Because -3 is negative you'll make it subtract.... I'll show you what I mean:
2m + 7 - 3 + 4m
Combine like terms (Terms which have the same variables... in this case the same number of m's)
