Add the cost of the three items:
8 + 5 + 15 = $28
Subtract that amount from the total:
29.82 - 28 = $1.82 ( amount he paid in tax)
Divide the tax amount by the cost of the items:
1.82 / 28 = 0.065
Multiply that by 100:
0.065 x 100 = 6.5% sales tax rate
