Question

What are the excluded values?
m +5
____________
mn + 3m

m = -5, n = -3
m = 0, n = -3
m = -3, n = 0

Answer 1

factor the bottom: (m)(n+3)

If m=0 you get 5/0 which is meaningless.
If n= -3 you get (m+5)/0 which is also meaningless.

Throw out m=0 and n=-3