Algebra 1

$b=-4$
We start with the given equation: $\frac{b}{13}-\frac{3b}{13}=\frac{8}{13}$ We multiply both sides by a common denominator, $13$, to clear the fractions from the equation: $13(\frac{b}{13}-\frac{3b}{13})=13(\frac{8}{13})$ $b-3b=8$ We combine like terms: $-2b=8$ We divide by $-2$ on both sides of the equation: $b=8/-2=-4$