GMAT Quantitative Reasoning Practice Test 1

Draw the $\mathit{x}$ - and $\mathit{y}$-axes, then plot the points and connect them.
The area of a trapezoid is ( base ${}_1^{}+$ base ${}_2^{})\times ($ height) $∕2$.
Base ${}_1^{}=5$, base ${}_2^{}=4$, height $=18$ thus the area is $9\times 9=81$.
The answer to the question is the square root of 81 , meaning 9 .