A telephone wire 15 meters long is threaded from the telephone pole, where it is fixed at a height of 8 meters from the ground

A telephone wire 15 meters long is threaded from the telephone pole, where it is fixed at a height of 8 meters from the ground to the house, where it is fixed at a height of 20 meters. Find the distance between the house and the post, assuming that the wire does not sag.

Let’s designate a telephone pole as CD, telephone wire – BC, house – AB, surface of the earth – AD. CD = 8, BC = 15, AB = 20. Let’s construct a straight line MS parallel AD. MB = AB-CD = 20-8 = 12
By the Pythagorean theorem:
CM ^ 2 = BC ^ 2-MB ^ 2 = 225-144 = 81
CM = 9
Answer: the distance between the house and the post is 9 meters