Answer:
The correct answer is to add 12 more white grapes to the mixture.
Explanation:
To begin with, the error in the mixture is due to the fact that there are 20 white grapes with 12 cherry halves stating that the mixture will not be good enough because the number of white grapes is not higher enough according to the rule that there must be 8 white grapes for every 3 cherry halves.
Secondly, to understand that rule, the person must divide the 12 cherry halves by 3, obtaining 4. That is the number that the person must multiplies the 8 white grapes to obtain a number that will balance the mixture according to the rule. Then if the person multiplies 8 by 4 he will obtain 32 and despiting the fact that the mixture already has 20 white grapes then it will only need to add 12 more to get the to number in which the mixture will be balanced.