To solve for x, you need to isolate/get the variable "x" by itself in the equation:
-4.5 = 1.5 - x Subtract 1.5 on both sides
-4.5 - 1.5 = 1.5 - 1.5 - x
-6 = -x Divide -1 on both sides to get "x" by itself
[two negative signs cancel each other out and become positive]
6 = x Your answer is D
You could have also done (without having to do division):
-4.5 = 1.5 - x Add x on both sides to make x positive
-4.5 + x = 1.5 - x + x
-4.5 + x = 1.5 Add 4.5 on both sides
-4.5 + 4.5 + x = 1.5 + 4.5
x = 6