Adding and Subtracting Rationals

Videos to help you:

http://www.educreations.com/lesson/view/subtracting-rationals/20019672/?ref=app

http://www.educreations.com/lesson/view/adding-rationals/20019397/?ref=app

Hint:

The common denominators for #8 - 5x(x-4); #10 - (x + 6)(x + 4); #12 - (x - 2)(x + 2)