Two sisters open savings accounts with $60 each that their grandmother gave them the first sister at $20 each month to her account. the second sister adds $40 every two months to her $60. if the sisters continue to make a deposits at the same rate, when will they have the same amount of money?

I am pretty sure they will have the same amount of money in two months, because if the first sister is putting in $20 to her $60 account every one month then every two months she will have $40 more in her account.  The second sister is putting in $40 to her $60 account every two months.  So I think they will have the same amount of money in two months.