Question 254412
You have a right triangle with one side=18 ft. & an hypotenuse=20 ft.
a^2+b^2=c62
18^2+b^2=2062
324+b^2=400
b^2=400-324
b^2=76 
b=sqrt76
b=8.7 or 9 ft. is the distance from the house to the base of the ladder.