A 20 ft ladder reaches a window 18 ft high. How far is the foot of the ladder from the base of the building?

Pythagoran theorem

length of ladder=hyptonuse

height of window is one leg

distance base is fram building is other leg

a²+b²=c²

c=hyp

a and b are legs

18²+b²=20²

324+b²=400

b²=76

b=2√19ft or aprox8.7178ft