Rearrange to
6ab+21b-8a-28 now factor 1st and 2nd pair of terms...
3b(2a+7)-4(2a+7)
(3b-4)(2a+7)
So it is the third one down...
Answer:
4) add 5x and 9x
answer: 14x - 30
7) subtract 28 from 15
answer: x - 13
Step-by-step explanation: sorry if it is wrong I try my best