HELP!!!

How can I calculate part a?
Thanks a lot

go hook jvc hgv cj xk jvc 6756

c.

step-by-step explanation:

because first you have to add the 4x, 9x, and the 7x together and you get 20x and then you add the last numbers up and you get 5and then you put the subtraction sign in there and that's how you get the answer.

i'm assuming that it's c.)   volcanoes built the mountains and earthquakes tore them down.