In each pear the first value is the regular price of an item and the second value is the price with gratuity. Identify the pair that does not belong with the other three $30,$34.50 $54,64.80 $16,$18.40 $90,$103.50
The price that does not belong is 16,18.40. You do this by finding the percent gratuity, which is 15%. All the other values have 15% gratuity except the $16.
