Answer
$b=-6\frac{2}{3}$
Work Step by Step
$\frac{3}{3b+4}=\frac{2}{b-4}$ cross multiply
$2(3b+4)=3(b-4)$ distributive property
$6b+8=3b-12$ subtract 3b from both sides; subtract 8 from both sides
$6b+8-3b-8=3b-12-3b-8$ combine like terms
$3b=-20$ divide both sides by 3
$3b\div3=-20\div3$ simplify
$b=-6\frac{2}{3}$
