There are 25% more green buttons than blue buttons in a bag. After Albert removed 40% of the green buttons and increased the number of blue buttons by 10%, there are now 126 fewer green buttons than blue buttons. Find the number of blue buttons at first.

	Green	Blue
Before	5 u	4 u
Change	- 2 u	+ 0.4 u
After	3 u	4.4 u

Number of green buttons in percentage
= 100% + 25%
= 125%

125% = ¹²⁵₁₀₀ = ⁵₄

Number of green buttons that Albert removed
= 40% x 5 u
= ⁴⁰₁₀₀ x 5 u 
= 2 u

Number of blue buttons that Albert increased 
= 10% x 4 u
= ¹⁰₁₀₀  x 4 u
= 0.4 u

Number of green buttons in the end
= 5 u - 2 u
= 3 u

Number of blue buttons in the end
= 4 u + 0.4 u
= 4.4 u

Number of fewer green buttons than blue buttons in the end
= 4.4 u - 3 u 
= 1.4 u 

1.4 u = 126

1 u = 126 ÷ 1.4 = 90

Number of blue buttons at first
= 4 u
= 4 x 90
= 360

Answer(s): 360