At the school, Storey A and Storey B had an equal number of chairs at first. If 9 chairs were removed from Storey B and 7 times as many chairs were removed from Storey A as Storey B, the number of chairs in Storey B would be 3 times as many as in Storey A. Find the number of chairs on each storey.

	Storey A	Storey B
Before	1 u	1 u
Change	- 63	- 9
After	1 u - 63	1 u - 9

Number of chairs removed from Storey A
= 7 x 9
= 63

Number of chairs on Storey A and Storey B at first is the same.

Number of chairs on Storey B is 3 times as many as Storey A in the end. If the number of chairs on Storey A increases by 3 times, the number of chairs on Storey A and Storey B will be the same.

3(1 u - 63) = 1 u - 9
3 u - 189 = 1 u - 9 
3 u - 1 u = 189 - 9
2 u = 180

1 u = 180 ÷ 2 = 90

Number of chairs in each floor
= 1 u
= 90

Answer(s): 90