## Algebra: A Combined Approach (4th Edition)

$-1$
Step 1: $\frac{7-x}{x-7}$ Step 2: $\frac{7-x}{-(-x+7)}$ Step 3: $\frac{7-x}{-(7-x)}$ Step 4: Cancelling the expression (7-x) as it is common to both the numerator and denominator, the expression becomes $\frac{1}{-1}=-1$.