Question

Please, I didn't understand you very well.

Answer 1

Check the picture below.

`\textit{area of a trapezoid}\\\\ A=\cfrac{h(a+b)}{2}~~ \begin{cases} h~~=height\\ a,b=\stackrel{parallel~sides}{bases~\hfill }\\[-0.5em] \hrulefill\\ A=20\\ b=6\\ h=4 \end{cases}\implies 20=\cfrac{4(a+6)}{2}\implies 40=4(a+6) \\\\\\ \cfrac{40}{4}=a+6\implies 10=a+6\implies 4=a`