Fill in the blank with a constant, so that the resulting expression can be factored as the product of two linear expressions: 2mn - 18m + 7n - 3mn + 15m + 8n + ___
Simplify as
-mn - 3m + 15n + ____
- m ( n + 3) + 15 (n + 3) =
( 15 - m) ( n + 3)
-mn - 3m + 15n + 45
+75 
