A 23.4 ounce shampoo bottle is labeled "Now 30% more free!" and sells for $15.00. What is the price per ounce of the original bottle?

We need to know how many ounces are in the original bottle.

If x is the original amount, then x + .3x = 23.4 oz

1.3x = 23.4

x = 23.4\1.3 = 18 oz

The price per ounce is $15.00 / 18 oz = $0.84