I'm so sorry if this is wrong but it might be 24.
Answer:
x+y/ 100 = 450
Step-by-step explanation:
450 = x% + y%
450 = x/100 + y/100
450 = x+y/100
Drake: 63 Mangoes
Rafael: 42 Mangoes
John: 84 Mangoes
Y=24 because 60/20 is 3. 3*8 is 24