In the standard $\displaystyle (x, y)$ coordinate plane, the coordinate of D are $\displaystyle (d, k)$ and the coordintate of E are $\displaystyle (e, k)$. When D is roated 180 degrees about E the result is F. In terms of d, e, and k, what are the coordinates of F?

The answer is $\displaystyle (2e - d, k)$ but I'm not sure to obtain to it :(