$$ \begin{aligned} 15 &= -8(5z+9)&& \text{simplify right side} \\[1 em]15 &= -(40z+72)&& \\[1 em]15 &= -40z-72&& \text{ swap the left and right side of the equation } \\[1 em]-40z-72 &= 15&& \text{ move -72 to the right } \\[1 em]-40z &= 15+72&& \\[1 em]-40z &= 87&& \text{ divide both sides by $ -40 $ } \\[1 em]z &= -\frac{87}{40}&& \\[1 em] \end{aligned} $$

This page was created using