## Geometry: Common Core (15th Edition)

$20\ cm^2$
If the height is $h$, the base is $3h-7$. Write an equation to find the height. $b=3h-7$ $5=3h-7\longrightarrow$ substitute the given base size $12=3h\longrightarrow$ addition property of equality $4=h\longrightarrow$ division property of equality $A=bh=5\times4=20$