There are 25% more white cards than black cards in a bag. After Reggie removed 20% of the white cards and increased the number of black cards by 30%, there are now 24 fewer white cards than black cards. Find the number of black cards at first.

	White	Black
Before	5 u	4 u
Change	- 1 u	+ 1.2 u
After	4 u	5.2 u

Number of white cards in percentage
= 100% + 25%
= 125%

125% = ¹²⁵₁₀₀ = ⁵₄

Number of white cards that Reggie removed
= 20% x 5 u
= ²⁰₁₀₀ x 5 u 
= 1 u

Number of black cards that Reggie increased 
= 30% x 4 u
= ³⁰₁₀₀  x 4 u
= 1.2 u

Number of white cards in the end
= 5 u - 1 u
= 4 u

Number of black cards in the end
= 4 u + 1.2 u
= 5.2 u

Number of fewer white cards than black cards in the end
= 5.2 u - 4 u 
= 1.2 u 

1.2 u = 24

1 u = 24 ÷ 1.2 = 20

Number of black cards at first
= 4 u
= 4 x 20
= 80

Answer(s): 80