\[\frac{b^{2} + 2b + 4}{3b - 4}\ :\frac{b^{3} - 8}{9b^{2} - 16} =\]
\[= \frac{\left( b^{2} + 2b + 4 \right)(3b - 4)(3b + 4)}{(3b - 4)(b - 2)\left( b^{2} + 2b + 4 \right)} =\]
\[= \frac{3b + 4\ }{b - 2}\]