15% of a 84.00 dollar jacket plus 7% sales tax
100-15=85
0.85×84=3575=71.4
100+7=107
1.07×71.4=76.398
$76.40
From what I understand, you mean you will get 15% off the price of the Jacket plus 7% sales tax.
So $84 - 15%(or .15 x 84)=$71.40 + 7%=$76.40 the final price you pay.