All you have to do is plug m and n into the equation:
n+6m
Since n=7, you'll get:
7+6m
And since m=8, you'll get:
7+6(8)
And by doing the order of operations (PEMDAS), you'll start off multiplying 6 and 8, which is 48, then add 7, which is 55.
Your answer should be 55!