$$ \begin{aligned} 15 \cdot \frac{x}{2} &= (6+x)\cdot\frac{6}{2}+6\cdot\frac{9}{2}&& \text{multiply ALL terms by } \color{blue}{ 2 }. \\[1 em]2\cdot15 \cdot \frac{x}{2} &= 2(6+x)\cdot\frac{6}{2}+2\cdot6\cdot\frac{9}{2}&& \text{cancel out the denominators} \\[1 em]15x &= 6x+36+54&& \text{simplify right side} \\[1 em]15x &= 6x+90&& \text{move the $ \color{blue}{ 6x } $ to the left side} \\[1 em]15x-6x &= 90&& \text{simplify left side} \\[1 em]9x &= 90&& \text{ divide both sides by $ 9 $ } \\[1 em]x &= \frac{90}{9}&& \\[1 em]x &= 10&& \\[1 em] \end{aligned} $$

This page was created using