80 A and 20 B are mixed together. By removing some A, the remaining A will be 75% of the mixture. How many A must be removed?
If 80 ml of A and 20 ml of B are mixed together: 100 ml total
x ml of A is taken out.
80-x = remaining A
% of A in new mixture is 0.75*(100-x)
so 80 - x = 75 - 0.75x
5 = (1/4)*x
x = 20ml
so amount of A removed is 20ml.
Hope I am not missing anything.
