The answer is the 16 - ounce bottle of shampoo for $7. This is how I did it:
I divided the price and the ounce of shampoo in the bottle.
\(24/9 = $2.67 per ounce\) and \(16/7 = $2.29 per ounce\)
Now you can see which one is a cheaper price. Hope this helped you =)
