If you do not see a number next to a variable, what is it understood to be?

It is assumed to only be 1 of said variable. For example, x=32. It is understood that "x" is equal to 1x

Step-by-step explanation:

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.