$$ \begin{aligned} 4x\cdot3+6x-7+3x\cdot3-5x\cdot2-5x+9 &= 0&& \text{simplify left side} \\[1 em]12x+6x-7+9x-10x-5x+9 &= 0&& \\[1 em]18x-7-6x+9 &= 0&& \\[1 em]12x+2 &= 0&& \text{ move the constants to the right } \\[1 em]12x &= -2&& \text{ divide both sides by $ 12 $ } \\[1 em]x &= -\frac{2}{12}&& \\[1 em]x &= -\frac{1}{6}&& \\[1 em] \end{aligned} $$

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