$$ \begin{aligned} 5x-3 &= 3x+6&& \text{move the $ \color{blue}{ 3x } $ to the left side and $ \color{blue}{ -3 }$ to the right} \\[1 em]5x-3x &= 6+3&& \text{simplify left and right hand side} \\[1 em]2x &= 9&& \text{ divide both sides by $ 2 $ } \\[1 em]x &= \frac{9}{2}&& \\[1 em] \end{aligned} $$