IF it's asking for how much money each person has...
x = eva
x + 7.50 = justin
(x + 7.50) - 12 = emma
therefore...
x + x + 7.50 + x + 7.50 - 12 = 63
combine like terms...
3x + 3 = 63
solve for x.
3x = 60
x = 20
therefore, eva has $20.
justin has $27.50
and Emma has $15.50