25) C

The one which has equal proportions (vinaigrette A) : 90 ml oil and 90 ml vinegar
90 ml of A would contain: 45 ml oil and 45 ml vinegar

90 ml of A is added to the second vinaigrette (B)
180 ml of B has: 120 ml oil (2/3) and 60 ml vinegar (1/3)

When 90 ml of A is added to 180 ml of B, total volume of new mixture = 180 + 90 = 270 ml
270 ml of the mixture has: (120 + 45) oil and (60 + 45) vinegar = 165 ml oil and 105 ml vinegar
Ratio of oil and vinegar = 33 / 21

90 ml of this mixture has: (165/3) oil and (105/3) vinegar = 55 ml oil and 35 ml vinegar
[We divided by 3 because the large mixture had 270 ml and we took out 90 ml. 270 / 90 = 3]

A now has: (45 + 55) oil and (45 + 35) = 100 ml oil and 80 ml vinegar
B now has: (165 – 55) oil and (105 – 35) = 110 ml oil and 80 ml vinegar

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