There are 25% more blue buttons than silver buttons in a bag. After Jenson removed 40% of the blue buttons and increased the number of silver buttons by 20%, there are now 90 fewer blue buttons than silver buttons. Find the number of silver buttons at first.

	Blue	Silver
Before	5 u	4 u
Change	- 2 u	+ 0.8 u
After	3 u	4.8 u

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

125% = ¹²⁵₁₀₀ = ⁵₄

Number of blue buttons that Jenson removed
= 40% x 5 u
= ⁴⁰₁₀₀ x 5 u 
= 2 u

Number of silver buttons that Jenson increased 
= 20% x 4 u
= ²⁰₁₀₀  x 4 u
= 0.8 u

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

Number of silver buttons in the end
= 4 u + 0.8 u
= 4.8 u

Number of fewer blue buttons than silver buttons in the end
= 4.8 u - 3 u 
= 1.8 u 

1.8 u = 90

1 u = 90 ÷ 1.8 = 50

Number of silver buttons at first
= 4 u
= 4 x 50
= 200

Answer(s): 200