A carpenter pounds a 0.002 kg nail into a board using a 1.0 kg hammer. If the hammer applies a force of 75N on the nail, what force does the nail apply onto the hammer?

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.