Given below are two quantities named A and B. Based on the given information, you have to determine the relationship between the two quantities. You should use the given data and your knowledge of Mathematics to choose between the possible answers.

Quantity A: There are two alloys in the first zinc, copper, and aluminium are in the ratio 3 : 4 : 5 and in the second alloy the ratio of zinc and copper is 1 : 2. If 24 kg of the first alloy and x kg of the second alloy are mixed, the amount of copper in the mixture becomes 20 kg. What is the value of x? 

Quantity B: 18 kg