B = 9
b = 7
A = 80
a = ?
Substitution
[tex]\begin{gathered} \text{ 80 = }\frac{(9\text{ + 7)}\cdot a}{2} \\ \text{ 80 = }\frac{16a}{2} \\ \text{ 80 = 8a} \\ \text{a = }\frac{80}{8} \\ a\text{ = 10 cm} \end{gathered}[/tex]The height of the trapezoid is 10 cm
