$$ \begin{aligned} -12x\cdot2-18x+77 &= -7x\cdot2-4&& \text{simplify left and right hand side} \\[1 em]-24x-18x+77 &= -14x-4&& \\[1 em]-42x+77 &= -14x-4&& \text{move the $ \color{blue}{ -14x } $ to the left side and $ \color{blue}{ 77 }$ to the right} \\[1 em]-42x+14x &= -4-77&& \text{simplify left and right hand side} \\[1 em]-28x &= -81&& \text{ divide both sides by $ -28 $ } \\[1 em]x &= \frac{-81}{-28}&& \\[1 em]x &= \frac{81}{28}&& \\[1 em] \end{aligned} $$

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