$$ \begin{aligned} 13-\frac{x}{20} &= \frac{58}{5}&& \text{multiply ALL terms by } \color{blue}{ 20 }. \\[1 em]20\cdot13-20 \cdot \frac{x}{20} &= 20\cdot\frac{58}{5}&& \text{cancel out the denominators} \\[1 em]260-x &= 232&& \text{ move 260 to the right } \\[1 em]-x &= 232-260&& \\[1 em]-x &= -28&& \text{switch signs on both sides} \\[1 em]x &= 28&& \\[1 em] \end{aligned} $$

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