Factor: 12x^2+13x-35

I need help on how you would go about doing this. I only understand when 1 is the coefficient for the x^2 term.

( ? x - 7) (? x + 5 )

first try
(3x-7)(4x+5) nope that is 12x^2-13x-35
but that makes it easy
(3x+7)(4x-5)