How does the author determine what this equation should be?
Mountainside fleece sold 40 neckwarmers. Solid color neckwarmers sold for $9.90 each and print ones sold for $12.75 each. In all, $421.65 ws taken in for the neckwarmers. How many of each type were sold?
In 2004, the Diabetic Express charged $27.06 for a vial of Humulin insulin and $34.39 for a vial of Novolin Velosulin insulin. If a total of $1565.57 was collected for 50 vials of insulin, how many vials of each type were sold?
Mountainside fleece sold 40 neckwarmers. Solid color neckwarmers sold for $9.90 each and print ones sold for $12.75 each. In all, $421.65 ws taken in for the neckwarmers. How many of each type were sold?
In 2004, the Diabetic Express charged $27.06 for a vial of Humulin insulin and $34.39 for a vial of Novolin Velosulin insulin. If a total of $1565.57 was collected for 50 vials of insulin, how many vials of each type were sold?