It form a right triangle legnth of ladder is hypotonuse bottom of ladder from wall distance is one leg distance up wall is other leg a^2+b^2=c^2 c=hypotonuse and a and b are legs
4^2+b^2=20^2 16+b^2=400 minus 16 both sides b^2=384 sqrt both sides b=8√6 ft aprox b=19.59ft from ground
