Subtract 7x-9 from 2x^2-11
a) 2x^2-7x-2
b) 2x^2+7x-20
c) 2x^2+7x-2

We keep the 2x^2 because we can only subtract something from that if it also is squared. From there, we subtract the 7x from 2x^2-11. Since there is no previous x's in the 2x^2-11, we just make it -7x. So, without even continuing the problem, we see that A) is the correct answer because it is the only one with -7x. 

It creates dogx^2 and then flip your answer and multiply by 2