$$ \begin{aligned} a+a\cdot\frac{8}{100} &= 168000&& \text{multiply ALL terms by } \color{blue}{ 100 }. \\[1 em]100a+100a\cdot\frac{8}{100} &= 100\cdot168000&& \text{cancel out the denominators} \\[1 em]100a+8a &= 16800000&& \text{simplify left side} \\[1 em]108a &= 16800000&& \text{ divide both sides by $ 108 $ } \\[1 em]a &= \frac{16800000}{108}&& \\[1 em]a &= \frac{1400000}{9}&& \\[1 em] \end{aligned} $$

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