Answer
b=-3
Work Step by Step
Use cross multiplication since the variable is on both sides of the proportion.
$\frac{b+13}{2}=\frac{-5b}{3}$ cross multiply
$3(b+13)=2(-5b)$ distributive property
$3b+39=-10b$ subtract 3b from both sides
$3b+39-3b=-10b-3b$ combine like terms
$39=-13b$ divide both sides by -13
$39\div-13=-13b\div-13$
$-3=b$
