so hmmm if you notice the tickmarks, the left-side is split in halves, and the right-side is also split in halves, that makes EF the midsegment of the trapezoid
thus [tex]\bf \textit{midsegment of a trapezoid}\\\\
m=\cfrac{base1+base2}{2}\qquad
\begin{cases}
base1, base2=\textit{parallel sides}\\
----------\\
base1=x+8\\
base2=58\\
m=6x
\end{cases}
\\\\\\
6x=\cfrac{(x+8)+(58)}{2}\implies 6x=\cfrac{x+8+58}{2}\implies 12x=x+66[/tex]
and surely you know how much that is
