## Precalculus (6th Edition) Blitzer

a. $H=\frac{7}{10}(220-a)$ $a= 20$ $H=\frac{7}{10}(220-20)=\frac{7}{10}(200)=7\times20=140$ b. $H=\frac{4}{5}(220-a)$ $a= 20$ $H=\frac{4}{5}(220-20)=\frac{4}{5}(200)=\frac{800}{5}=160$