well, the shape is a trapezoid, a trapezoid has two parallel sides only, the parallel sides are called "bases", and the distance between the parallel sides is its "height".
so in the trapezoid above, it has two parallel sides, 20 m and 8 m, and the height or distance between both is 7 m, so
[tex]\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=8\\ h=7 \end{cases}\implies \begin{array}{llll} A=\cfrac{7(20+8)}{2}\implies A=\cfrac{7(28)}{2} \\\\\\ A=7(14)\implies A=98~m^2 \end{array}[/tex]