Final answer:
A box of Butterfingers costs approximately $9.83, and a box of Kit Kats costs approximately $6.83.
Step-by-step explanation:
Let's assume the cost of a box of Butterfingers is x dollars. We know that a box of Kit Kats costs $3 less, so the cost of a box of Kit Kats is (x-3) dollars.
The family purchased 7 boxes of Butterfingers, so the total cost of the Butterfingers is 7x dollars. They also purchased 5 boxes of Kit Kats, so the total cost of the Kit Kats is 5(x-3) dollars.
The total cost of both candies is given as $103, so we can set up the equation: 7x + 5(x-3) = 103.
Solving this equation, we get 7x + 5x - 15 = 103, which simplifies to 12x - 15 = 103.
Adding 15 to both sides, we get 12x = 118. Dividing both sides by 12, we find that x = 9.83.
Therefore, a box of Butterfingers costs approximately $9.83, and a box of Kit Kats costs approximately $6.83.