$$ \begin{aligned} x+5\cdot(3+x) &= 3 \cdot \frac{x}{2}-9&& \text{multiply ALL terms by } \color{blue}{ 2 }. \\[1 em]2x+2\cdot5\cdot(3+x) &= 2\cdot3 \cdot \frac{x}{2}-2\cdot9&& \text{cancel out the denominators} \\[1 em]2x+10x+30 &= 3x-18&& \text{simplify left side} \\[1 em]12x+30 &= 3x-18&& \text{move the $ \color{blue}{ 3x } $ to the left side and $ \color{blue}{ 30 }$ to the right} \\[1 em]12x-3x &= -18-30&& \text{simplify left and right hand side} \\[1 em]9x &= -48&& \text{ divide both sides by $ 9 $ } \\[1 em]x &= -\frac{48}{9}&& \\[1 em]x &= -\frac{16}{3}&& \\[1 em] \end{aligned} $$

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