In solving this type of problem always look for the person you don't have any information about in this case it's Eve therefore Eve is X, Justin has $7.50 more than Eve, therefore
X+$7.50 is Justin and Emma has $12 less than Justin, therefore subtract $12 from Justin X+$7.50-$12, since the total amount is $63 add all the numbers and equal them to $63.
x+7+x+7.5-12+ x=63
3x+3=63
3x=60
x=20
Plug in the x for each person
therefore Eve=$20
Justin=$20+$7.50= $27.50
Emma has $12 less than Justin therefore $15.50
Add all the money and it equals $63