Answer:
16 feet
Step-by-step explanation:
The length of the ladder=20 feet
Distance from the base of the ladder to the house = 12 feet
You will notice that a wall is vertical and the ladder makes an angle with the horizontal ground(making it the hypotenuse). This is a right triangle problem.
To find the how far up the house can the ladder can reach, we simply find the third side of the right triangle.
From Pythagoras theorem
The third side of the right triangle is 16. Therefore the ladder leans 16 feet from the ground.