Heres the question: Secants $\displaystyle ABC$ and $\displaystyle ADE$ intersect at point $\displaystyle A$ outside the circle. If $\displaystyle AC=20, AB=5, AD=4$, find $\displaystyle AE$.

Okay so i did

$\displaystyle 20*5=4*x$

$\displaystyle 100=4x$

$\displaystyle 100/4=4x/4$

$\displaystyle x=25$

Okay so my question is, is the answer $\displaystyle 25$ or do i subtract $\displaystyle 4$ from it?