help

We know that $\triangle BDF$ and $\triangle ECF$ have the same area, and adding the area of quadrilateral $ABFE$ to each of them shows us that $$\text{(area of $\triangle ADE$)}=\text{(area of $\triangle ABC$)}.$$ Using the area formula for triangles, we can turn the last equation into $$\dfrac{1}{2}\cdot AD\cdot AE = \dfrac{1}{2}\cdot AB\cdot AC.$$ Substituting in the given lengths, we get $$\dfrac{1}{2}\cdot 5\cdot 4 = \dfrac{1}{2}\cdot 3\cdot AC,$$ so $AC=\dfrac{20}{3}$. We compute the length we are interested in as $EC=AC-AE=\dfrac{20}{3}-4=\boxed{\dfrac{8}{3}}$.

You know it's best not to assume.

AE is 4 so -AE=-4

https://web2.0calc.com/questions/help-please_90002

This link shows the complete question, and my answer is there (post #2)