Answer
He saves 9.12 feet (correct to 3 significant figures)
Work Step by Step
Using Pythagorean Theorem,
$20^{2}$ = $(x+8)^{2}$ + $x^{2}$
2$x^{2}$ + 16x + 64 = 400
$x^{2}$ + 8x - 168 = 0
x = 9.56 (corr. to 3 sig fig)
He saves 29.12 - 20 feet