Question

1. $\frac{9}{4}=\frac{r - 10}{r}$

Explanation:

Step1: Cross - multiply

$9r = 4(r - 10)$

Step2: Expand the right side

$9r=4r - 40$

Step3: Subtract 4r from both sides

$9r-4r=4r - 40-4r$
$5r=-40$

Step4: Solve for r

$r=\frac{-40}{5}=-8$

Answer:

$r = - 8$