The answer to your problem would be -8
I got this because if you take 4 - 2x to the third power, it would look like this:
(4 - 2x)^3
All you have to do it plug in 3, solve for the equation in the parentheses, and then take that number to the third power. In this case, you get -2, and if you take that to the third power, you get -8.
Hope this helps!
