How do i do these types of problems? (and how do i do this one specifically)

This is basically a part of PEMDAS.

First, you must do the parenthesis part, meaning to find the answer inside the parenthesis first.

Subtract 13.5–4.5 to get rid of the parenthesis. You get 9.

Now, finish the equation off: 5·9 (five times nine). You end up with 45.

-2x + 7 = 7

subtract 7 from both sides.

-2x = 0

divide both sides by -2.

x = 0

the value of x is equal to 0.