Answer
$b=20$
Work Step by Step
We are given the equation $-\frac{9}{10}b=-18$. Multiply both sides by $-\frac{10}{9}$.
$(-\frac{9}{10}b\times-\frac{10}{9})=b=-18\times-\frac{10}{9}=\frac{18\times10}{9}=\frac{180}{9}=20$
Therefore, $b=20$.