$$ \begin{aligned} -76 &= -3b-49&& \text{ swap the left and right side of the equation } \\[1 em]-3b-49 &= -76&& \text{ move -49 to the right } \\[1 em]-3b &= -76+49&& \\[1 em]-3b &= -27&& \text{ divide both sides by $ -3 $ } \\[1 em]b &= \frac{-27}{-3}&& \\[1 em]b &= 9&& \\[1 em] \end{aligned} $$