Answer:
b=17.75 ft
Step-by-step explanation:
We will answer this using Pythagorean Theorem.
Since the bottom of a ladder is 3 feet from the wall, and the ladder is 18 ft long, the ladder is the hypotenuse. Knowing pythagorean theorem (a^2+b^2=c^2), we can plug it in.
3^2 + b^2 = 18^2
9+b^2=324
b^2=315
b=17.75 ft
