# How do you simplify (3b)/(b(b+9))?

$\frac{3}{b + 9}$
Cancel the $b$'s to get $\frac{3 b}{b \left(b + 9\right)} = \frac{3 \setminus \cancel{b}}{\setminus \cancel{b} \left(b + 9\right)} = \frac{3}{b + 9}$.
These are equal as long as $b \ne 0$.