$$ \begin{aligned} 3x-(2x-1) &= -9x-1&& \text{simplify left side} \\[1 em]3x-2x+1 &= -9x-1&& \\[1 em]x+1 &= -9x-1&& \text{move the $ \color{blue}{ -9x } $ to the left side and $ \color{blue}{ 1 }$ to the right} \\[1 em]x+9x &= -1-1&& \text{simplify left and right hand side} \\[1 em]10x &= -2&& \text{ divide both sides by $ 10 $ } \\[1 em]x &= -\frac{2}{10}&& \\[1 em]x &= -\frac{1}{5}&& \\[1 em] \end{aligned} $$

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