Red and White Marbles

There are only red and white marbles in the bag, and precisely 18% of the marbles in the bag are red. After removing 25 white balls, exactly 20% of the balls in the bag will be red. How many balls are there?
very much for your help

Final Answer:

b =  205
c =  45

Step-by-step explanation:


c = 18/100 · (c+b)
c = 20/100 · (c+b-25)

18b-82c = 0
20b-80c = 500

Pivot: Row 1 ↔ Row 2
20b-80c = 500
18b-82c = 0

Row 2 - 18/20 · Row 1 → Row 2
20b-80c = 500
-10c = -450


c = -450/-10 = 45
b = 500+80c/20 = 500+80 · 45/20 = 205

b = 205
c = 45

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