4285.68 / 3 = 1428.56
(You divide by 3 since Steven deposited a third into his savings account. You're trying to find out how much a third is.)
4285.68 - 1428.56 = 2857.12
(You subtract a third from the total because after Steven deposited a third, there are two thirds left, and you're trying to figure out how much that two thirds is since it went into his checking)
It ends up being $2,857.12