$$ \begin{aligned} 9 \cdot \frac{r}{5-r} &= 95&& \text{multiply ALL terms by } \color{blue}{ 5-r }. \\[1 em](5-r)\cdot9 \cdot \frac{r}{5-r} &= (5-r)\cdot95&& \text{cancel out the denominators} \\[1 em]9r &= -95r+475&& \text{move the $ \color{blue}{ -95r } $ to the left side} \\[1 em]9r+95r &= 475&& \text{simplify left side} \\[1 em]104r &= 475&& \text{ divide both sides by $ 104 $ } \\[1 em]r &= \frac{475}{104}&& \\[1 em] \end{aligned} $$

This page was created using