## Intermediate Algebra for College Students (7th Edition)

$15$ mph
distance = (rate)$\times$(time) $\Rightarrow$ time = $\displaystyle \frac{\text{distance}}{\text{rate}}$ Let x be the rate of the bicyclist in calm air. We are given: $\displaystyle \frac{75}{x+10}=\frac{15}{x-10} \qquad$ ... $/\times(x+10)(x-10)$ $75(x-10)=15(x+10)$ $75x-750=15x+150\qquad$ ... add $750- 15x$ $60x=900\qquad$ ...$/\div 60$ $x=15$mph rate of the bicyclist in calm air = $15$ mph