Again using the Pythagorean Theorem:
h^2=x^2+y^2, where h is the hypotenuse of a right triangle and x and y are the side lengths. You are given that the hypotenuse is 34 ft and the base side is 16ft. Let h=34, x=16, and y=height, then you have:
34^2=16^2+y^2
y^2=34^2-16^2
y^2=1156-256
y^2=900
y=√900
y=30 ft
So the ladder will reach a spot 30 feet high on the building.