I'd strongly suggest that you write this fraction as
m+n
------
9m
Otherwise it's difficult to be sure what's being divided and what's not.
Alternatively: (m + n) / 9m.
Subbing 4 for m and 36 for n, we get:
10
40 / 36 = ------
9
If this disagrees with your answer choices, it's because of the ambiguity regarding what you are multiplying and/or dividing.