Question 298203
If Jack earns X $, Mary Y $, Jill Z $ then:

X = 2 * Y

And 

Z = Y + 8


if Y = 5 then X =10 while Z =13 which means Jill makes the most money but if Y = 20 e.g. then X = 40 while Z = 28 then in this case it is Jack who makes the most money.

So we can't conclusively state who makes the most money with the information provided