## Precalculus (6th Edition) Blitzer

$b=2$
If the solution set is $\{-6\}$, by substituting $x=-6$ into the equation, it should be true. $\displaystyle \frac{7(-6)+4}{b}+13=-6\qquad$ ... we now solve this for b ... subtract 13 $\displaystyle \frac{-38}{b}=-19\qquad$ ... multiply with b $-38=-19b\qquad$ ... divide with $-19$ $b=2$