There are 25% more blue stamps than red stamps in a bag. After David removed 20% of the blue stamps and increased the number of red stamps by 20%, there are now 16 fewer blue stamps than red stamps. Find the number of red stamps at first.

	Blue	Red
Before	5 u	4 u
Change	- 1 u	+ 0.8 u
After	4 u	4.8 u

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

125% = ¹²⁵₁₀₀ = ⁵₄

Number of blue stamps that David removed
= 20% x 5 u
= ²⁰₁₀₀ x 5 u 
= 1 u

Number of red stamps that David increased 
= 20% x 4 u
= ²⁰₁₀₀  x 4 u
= 0.8 u

Number of blue stamps in the end
= 5 u - 1 u
= 4 u

Number of red stamps in the end
= 4 u + 0.8 u
= 4.8 u

Number of fewer blue stamps than red stamps in the end
= 4.8 u - 4 u 
= 0.8 u 

0.8 u = 16

1 u = 16 ÷ 0.8 = 20

Number of red stamps at first
= 4 u
= 4 x 20
= 80

Answer(s): 80