D= Daniel
J= Jessica
D + J = 31
D + (D-9) = 31
Jessica has 9 less than Daniel, so you have to subtract 9 from the amount Daniel has.
2D - 9 = 31
add 9 to both sides
2D=40
divide both sides by 2
D=20
J = D-9 = 20-9 = 11
To check your answer, add Daniel's money and Jessica's money and it should equal their total amount of money.
20 + 11 = 31
Hope this helps!! :)
