$$ \begin{aligned} 4x-3 &= 5+3x&& \text{move the $ \color{blue}{ 3x } $ to the left side and $ \color{blue}{ -3 }$ to the right} \\[1 em]4x-3x &= 5+3&& \text{simplify left and right hand side} \\[1 em]x &= 8&& \\[1 em]x &= 8&& \\[1 em] \end{aligned} $$