$$ \begin{aligned} 3x+2 &= 1-x&& \text{move the $ \color{blue}{ -x } $ to the left side and $ \color{blue}{ 2 }$ to the right} \\[1 em]3x+x &= 1-2&& \text{simplify left and right hand side} \\[1 em]4x &= -1&& \text{ divide both sides by $ 4 $ } \\[1 em]x &= -\frac{1}{4}&& \\[1 em] \end{aligned} $$