-2x(3-x) in distributive property..

You have to multiply the first term, -2x, by each of the terms within the parentheses. So it will look like this:

-2x*3 - -2x*x, and then you clean it up to: -6x +2x^2 (That's x squared). Notice that the sign in the middle changed because you are subtracting a negative term, which is the same as adding.