Answer
At \$0.175/ounce after the coupon, Brand P is the best buy.
Work Step by Step
After subtracting the coupon savings, find the cost per unit for each brand.
Brand G $\frac{(2.39 - 0.60)}{10 ounces}$ = $\frac{1.79}{10 ounces}$ = $\frac{1.79\div10}{10\div10 ounces}$ = $\frac{0.179}{1 ounce}$ = 0.179/ounce
Brand K $\frac{3.99}{20.3 ounces}$ = $\frac{3.99\div20.3}{20.3\div20.3 ounces}$ = $\frac{0.197}{1 ounce}$ = 0.197/ounce
Brand P $\frac{(3.39 - 0.50)}{16.5 ounces}$ = $\frac{2.89}{16.5 ounces}$ = $\frac{2.89\div16.5}{16.5\div16.5 ounces}$ = $\frac{0.175}{1 ounce}$ = 0.175/ounce