$$ \begin{aligned} \frac{2}{5}x+8 &= \frac{1}{5}x+4&& \text{multiply ALL terms by } \color{blue}{ 5 }. \\[1 em]5 \cdot \frac{2}{5}x+5\cdot8 &= 5 \cdot \frac{1}{5}x+5\cdot4&& \text{cancel out the denominators} \\[1 em]2x+40 &= x+20&& \text{move the $ \color{blue}{ x } $ to the left side and $ \color{blue}{ 40 }$ to the right} \\[1 em]2x-x &= 20-40&& \text{simplify left and right hand side} \\[1 em]x &= -20&& \\[1 em]x &= -20&& \\[1 em] \end{aligned} $$

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