$$ \begin{aligned} 14\cdot(20-4a) &= 6-a&& \text{simplify left and right hand side} \\[1 em]280-56a &= -a+6&& \\[1 em]-56a+280 &= -a+6&& \text{move the $ \color{blue}{ -a } $ to the left side and $ \color{blue}{ 280 }$ to the right} \\[1 em]-56a+a &= 6-280&& \text{simplify left and right hand side} \\[1 em]-55a &= -274&& \text{ divide both sides by $ -55 $ } \\[1 em]a &= \frac{-274}{-55}&& \\[1 em]a &= \frac{274}{55}&& \\[1 em] \end{aligned} $$

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