Answer: $77.40
Explanation:
First you take the 7.5% and turn it into a decimal and to do that you have to divide 7.5 by 100 which gives you .075. You then multiply 72 by .075 to know how much money you will pay with tax and you get $5.40. then you add $5.40 to $72 to get the total coast of the battery, which is $77.40.
The total cost of the battery was $77.40.