$$ \begin{aligned} 4(\frac{x}{8}-\frac{1}{9}) &= 20&& \text{simplify left side} \\[1 em]4 \cdot \frac{9x-8}{72} &= 20&& \\[1 em]\frac{36x-32}{72} &= 20&& \text{multiply ALL terms by } \color{blue}{ 72 }. \\[1 em]72 \cdot \frac{36x-32}{72} &= 72\cdot20&& \text{cancel out the denominators} \\[1 em]36x-32 &= 1440&& \text{ move -32 to the right } \\[1 em]36x &= 1440+32&& \\[1 em]36x &= 1472&& \text{ divide both sides by $ 36 $ } \\[1 em]x &= \frac{1472}{36}&& \\[1 em]x &= \frac{368}{9}&& \\[1 em] \end{aligned} $$

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