Claire purchases a new dress for the prom. the dress is priced $160, but it is on sale for 30% off. claire’s aunt works at the store and can give her an additional 10% off.
if the sales tax is 7.5%, how much does claire pay for the dress?
a. $93.24
b. $103.20
c. $108.36
d. $120.40

If you would like to know how much does Claire pay for the dress, you can calculate this using the following steps:

on sale for 30% off:
30% of $160 = 30% * 160 = 30/100 * 160 = $48
$160 - $48 = $112

an additional 10% off:
10% of $112 = 10% * 112 = 10/100 * 112 = $11.2
$112 - $11.2 = $100.8

the sales tax ... 7.5%
7.5% of $100.8 = 7.5% * 100.8 = 7.5/100 * 100.8 = $7.56
$100.8 + $7.56 = $108.36

The correct result would be c. $108.36.

What am i doing here. add?