Answer
$\frac{3 - b}{b - 3}$
Work Step by Step
Since we already have common denominators, we can add and simplify the numerators:
$\frac{3}{b - 3} - \frac{b}{b-3} =\frac{3 - b}{b - 3}$
$3-b \ne b-3$, so these cannot cancel out as common factors.
