Joyce and Tina had an equal amount of money
Lets x = # of days they spent money
Joyce spent $24 still had $64 left = 24x + 64
Tina spent $28 a day and spent all her money, no left = 28x
Both has equal amount of money so
28x = 24x + 64
Subtract 24x from both sides
4x = 64
Divide both sides by 4
x = 16
Answer:
Tina spent all her money in 16 days.