One way to do it is to divide $5460.40 by 8 so we will find out how much is 1/8 of that sum:
5460.40 / 8 = 682,55
Now 3/8 of the sum is 682,55 * 3 = 2047,65. That's how much Gavin deposited into a savings account.
5460,40 - 2047,65 = 3412,75. That's 5/8 of his money which went to his checking account.