$$ \begin{aligned} \frac{3}{4}x-1 &= 20&& \text{multiply ALL terms by } \color{blue}{ 4 }. \\[1 em]4 \cdot \frac{3}{4}x-4\cdot1 &= 4\cdot20&& \text{cancel out the denominators} \\[1 em]3x-4 &= 80&& \text{ move -4 to the right } \\[1 em]3x &= 80+4&& \\[1 em]3x &= 84&& \text{ divide both sides by $ 3 $ } \\[1 em]x &= \frac{84}{3}&& \\[1 em]x &= 28&& \\[1 em] \end{aligned} $$

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