The middle number is -3 and the last number is -10.

Factoring means we want something like

(x+_)(x+_)

Which numbers go in the blanks?

We need two numbers that...

Add together to get -3

Multiply together to get -10

Can you think of the two numbers?

Try 2 and -5:

2+-5 = -3

2*-5 = -10

Fill in the blanks in

(x+_)(x+_)

with 2 and -5 to get...

(x+2)(x-5)

Answer: (x+2)(x-5)