Question

If the area of quadrilateral SODA is 60, find the value for a.

Answer 1

$\textit{area of a rectangle}\\\\ A=Lw ~~ \begin{cases} L=length\\ w=width\\[-0.5em] \hrulefill\\ L=a+5\\ w=a-2\\ A=60 \end{cases}\implies 60=(a+5)(a-2) \\\\\\ 60=\stackrel{F~O~I~L}{a^2+3a-10}\implies 0=a^2+3a-70 \\\\\\ 0=(a+10)(a-7)\implies a= \begin{cases} -10\\\\ 7 ~~ \textit{\LARGE \checkmark} \end{cases}$

notice, we didn't use the negative value, valid though as it is, because in this case "a" can't be negative.