$$ \begin{aligned} -10-5r+7r &= 10-8(-4r-5)&& \text{simplify left and right hand side} \\[1 em]2r-10 &= 10-(-32r-40)&& \\[1 em]2r-10 &= 10+32r+40&& \\[1 em]2r-10 &= 32r+50&& \text{move the $ \color{blue}{ 32r } $ to the left side and $ \color{blue}{ -10 }$ to the right} \\[1 em]2r-32r &= 50+10&& \text{simplify left and right hand side} \\[1 em]-30r &= 60&& \text{ divide both sides by $ -30 $ } \\[1 em]r &= -\frac{60}{30}&& \\[1 em]r &= -2&& \\[1 em] \end{aligned} $$
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