$$ \begin{aligned} 5x+\frac{3}{4} &= 12&& \text{multiply ALL terms by } \color{blue}{ 4 }. \\[1 em]4\cdot5x+4\cdot\frac{3}{4} &= 4\cdot12&& \text{cancel out the denominators} \\[1 em]20x+3 &= 48&& \text{ move 3 to the right } \\[1 em]20x &= 48-3&& \\[1 em]20x &= 45&& \text{ divide both sides by $ 20 $ } \\[1 em]x &= \frac{45}{20}&& \\[1 em]x &= \frac{9}{4}&& \\[1 em] \end{aligned} $$

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