$$ \begin{aligned} 4+\frac{12}{2}x\cdot3-9 &= 0&& \text{multiply ALL terms by } \color{blue}{ 2 }. \\[1 em]2\cdot4+2 \cdot \frac{12}{2}x\cdot3-2\cdot9 &= 2\cdot0&& \text{cancel out the denominators} \\[1 em]8+36x-18 &= 0&& \text{simplify left side} \\[1 em]36x-10 &= 0&& \text{ move the constants to the right } \\[1 em]36x &= 10&& \text{ divide both sides by $ 36 $ } \\[1 em]x &= \frac{10}{36}&& \\[1 em]x &= \frac{5}{18}&& \\[1 em] \end{aligned} $$

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