Answer:
15
Explanation:
The ratio of (the foot of the ladder to the person) : (the person's height) is equal to (the wall to the foot of the ladder) : (the height of the wall) because the triangles are similar. So, if you solve the problem you will get:
(x= the height of the wall)
6:6 = 6+9:x
6:6 = 15:x
1:1=15:x
x=15
The height of the wall is 15 feet.