Frank paid a total of $304 ($55+249). You multiply $304 by 0.07 to get $21.28 (To convert a number to a percentage, multiply it by 100. So, 0.07 as a percent is equal to 7%). You add this to $304 to get to your answer: $325.28.
The total would be $325.28 if the sunglasses were $249. Hope it helped!
