Justin has $7.50 more than eva and emma has $12 less than justin. together, they have a total of 63.00$. how much money does each person?

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