\[\frac{3b + 7^{\backslash b}}{3b} - \frac{b^{2} - 5^{\backslash 3}}{b^{2}} =\]
\[= \frac{3b^{2} + 7b - 3b^{2} + 15}{3b^{2}} =\]
\[= \frac{7b + 15}{3b^{2}}.\]