Factor the expression:
2x(x - 3) + 7(x - 3)

Isnt it 2x^2+x-21
Im not sure but you need to do
This

When you see a common factor in a polynomial, you should see immediately that you can take that factor out, and multiply it on to the remaining terms.

You can see this can be written as:

(x-3)(2x+7)

Just see it as distributing one term onto another.