Answer:
-10
Step-by-step explanation:
First we need to factor the two first terms of the expression:
3mn - 6m = 3m * (n - 2)
Then, if we want to find in the end a product of two linear factors, we need the other two terms of the expression to have a common term of (n-2).
If the third term is 5n and the factors need to be linear, we can have 5 as the common factor:
5 * (n-2) = 5n - 10
So the fourth term is -10, then we would have:
3mn - 6m + 5n - 10
3m * (n - 2) + 5 * (n - 2)
(3m + 5) * (n - 2)
