$$ \begin{aligned} \frac{1}{5}(20y-15) &= 7y+9&& \text{simplify left side} \\[1 em]\frac{20y-15}{5} &= 7y+9&& \text{multiply ALL terms by } \color{blue}{ 5 }. \\[1 em]5 \cdot \frac{20y-15}{5} &= 5\cdot7y+5\cdot9&& \text{cancel out the denominators} \\[1 em]20y-15 &= 35y+45&& \text{move the $ \color{blue}{ 35y } $ to the left side and $ \color{blue}{ -15 }$ to the right} \\[1 em]20y-35y &= 45+15&& \text{simplify left and right hand side} \\[1 em]-15y &= 60&& \text{ divide both sides by $ -15 $ } \\[1 em]y &= -\frac{60}{15}&& \\[1 em]y &= -4&& \\[1 em] \end{aligned} $$

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