Answer:
13.7 feet
Step-by-step explanation:
The ladder and the building will form a right triangle with the ladder's length is hypotenuse
so if a is the height of the building
c^2 = a^2 + b^2
(15)^2 = a^2 + (6)^2
225 = a^2 + 36
a^2 = 225 - 36 = 189
a = √(189 = 13.7
