$$\frac{400}{x}+\frac{400}{x}+5 = 4$$

$$ \begin{aligned} \frac{400}{x}+\frac{400}{x}+5 &= 4&& \text{multiply ALL terms by } \color{blue}{ x }. \\[1 em]x\cdot\frac{400}{x}+x\cdot\frac{400}{x}+x\cdot5 &= x\cdot4&& \text{cancel out the denominators} \\[1 em]400+400+5x &= 4x&& \text{simplify left side} \\[1 em]5x+800 &= 4x&& \text{move the $ \color{blue}{ 4x } $ to the left side and $ \color{blue}{ 800 }$ to the right} \\[1 em]5x-4x &= -800&& \text{simplify left side} \\[1 em]x &= -800&& \\[1 em]x &= -800&& \\[1 em] \end{aligned} $$

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