Since Laura sold 4 more than Rebecca, you subtract 4 from 45 which is 41, and Rebecca sold 11 more than Chad, you subtract 11 from 41 which is 30. Laura sold 45 magazine. Rebecca sold 41 magazine. Chad sold 30 magzine.
Size 40 is the cheapest, because the formula to find lowest price of unit is dividing the price by the unit. so 5.49/24≈ 0.23, 8.00/40=0.2, 15.99/64≈ 0.25
