5(x- _) (x+4) = 5x²+_x-60
The first blank needs a vaiue such that when it is multiplied by 4, the result is -30. 15 is what we need. But there is a 5 in front of the expression, so the value inside should be a 3.
5(x- 3) (x+4) = 5x²+_x-60
Multiply the two expressions and we'll find
(5x- 15) (x+4) = 5x²+5x-60