Answer: C. 17.5 feet
Step-by-step explanation:
The attached photo shows the triangle ABC formed by the ladder and the wall. It is a right angle triangle because one of its angles is 90 degrees. The ladder is the hypotenuse of the triangle. To determine the height of the wall, we would find BC by applying Pythagoras theorem
Hypotenuse^2 = opposite ^2 + adjacent^2
18^2 + 4.5^2 + BC^2
BC^2 = 324 - 20.25 = 303.75
BC = √303.75 = 17.5 feet.
