$$ \begin{aligned} 7 &= \frac{3}{4}(7x+20)&& \text{simplify right side} \\[1 em]7 &= \frac{21x+60}{4}&& \text{multiply ALL terms by } \color{blue}{ 4 }. \\[1 em]4\cdot7 &= 4 \cdot \frac{21x+60}{4}&& \text{cancel out the denominators} \\[1 em]28 &= 21x+60&& \text{ swap the left and right side of the equation } \\[1 em]21x+60 &= 28&& \text{ move 60 to the right } \\[1 em]21x &= 28-60&& \\[1 em]21x &= -32&& \text{ divide both sides by $ 21 $ } \\[1 em]x &= -\frac{32}{21}&& \\[1 em] \end{aligned} $$

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