Question 1010990
Make yourself a right triangle.
Call the hypotenuse, x, which is the length of the ladder.
The leg going up is x-9.
The base is 15 feet.
Use the Pythagrean Theorem and solve for x...
15^2 + (x-9)^2 = x^2
225 + x^2 - 18x + 81 = x^2
306 = 18x
x = 17 feet