#### Answer

$-\frac{1}{2}$

#### Work Step by Step

We factor the expressions in order to cancel out common factors in the numerator and the denominator:
Step 1: $\frac{5x-40}{80-10x}$
Step 2: $\frac{5(x-8)}{-10(x-8)}$
Step 3: $\frac{5}{-10}$
Step 4: $-\frac{1}{2}$