There was an equation I was stuck on;

5x-3(x+2)=-12 solve for x.
I tried working on it and got left with 5x squared is = to -6 but didn't know what to do after that? Please help

I don't see any x^2 anywhere in there

5x-3(x+2) = -12
5x-3x-6 = -12
2x = -6
x = -3