Answer:
Perpendicular bisector theorem
Step-by-step explanation:
The illustration of the theorem is:
If point B is a perpendicular bisector of Line AC and the length of AC is 10cm
Then

Where
--- Perpendicular bisector
So, the equation becomes



Recall: 

60.
The question gives you the fact that 6 bricks is 2 feet high.
What do you do to get from 2 to 20?
You multiply by 10.
Since you multiplied one thing by 10, you must do it to the other side so it remains balanced.
2 ft x 10ft = 20ft
6 bricks x 10 bricks = 60 bricks