$$ \begin{aligned} 12-\frac{1}{4}x &= 7&& \text{multiply ALL terms by } \color{blue}{ 4 }. \\[1 em]4\cdot12-4 \cdot \frac{1}{4}x &= 4\cdot7&& \text{cancel out the denominators} \\[1 em]48-x &= 28&& \text{ move 48 to the right } \\[1 em]-x &= 28-48&& \\[1 em]-x &= -20&& \text{switch signs on both sides} \\[1 em]x &= 20&& \\[1 em] \end{aligned} $$

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