Help With Problem Solving...Am I Correct

This is the homework problem:
Use the five steps for problem solving to answer the following question. Please show all of your work.
Angle M and Angle N are supplementary angles. If Angle M is nine more than one half angle N, what are the measures of the angles?

My answer:
m + n =180
m = n/2 + 9
2m = n + 18 multiply each side by 2
n = 2m -18
m + 2m - 18 = 180 Substitute 2m-18 for n

3m = 198
m = 66
n = 114

M + N = 180

M = N/2 + 9
2M = N + 18
2M - 18 = N

M + 2M - 18 = 180
3M = 198
M = 66°
N = 114°

great job. Perfect.

Yes, you are. Your method and answer is correct. Congratulations!