Answer
$-1$
Work Step by Step
Step 1: $\frac{x-3}{3-x}$
Step 2: $\frac{x-3}{-x+3}$
Step 3: $\frac{x-3}{-(x-3)}$
Step 3: Since the numerator and denominator both contain (x-3), they can be cancelled to give $\frac{1}{-1}$
Step 4: $\frac{1}{-1}$=$-1$