$$ \begin{aligned} 66 \cdot \frac{x}{3}\cdot(21+1) &= 0&& \text{simplify left side} \\[1 em]66 \cdot \frac{x}{3}\cdot22 &= 0&& \\[1 em]\frac{66x}{3}\cdot22 &= 0&& \\[1 em]\frac{1452x}{3} &= 0&& \text{multiply ALL terms by } \color{blue}{ 3 }. \\[1 em]3 \cdot \frac{1452x}{3} &= 3\cdot0&& \text{cancel out the denominators} \\[1 em]1452x &= 0&& \text{ divide both sides by $ 1452 $ } \\[1 em]x &= \frac{0}{1452}&& \\[1 em]x &= 0&& \\[1 em] \end{aligned} $$

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