The total cost of the art supplies without the coupon is:
2 paint brushes x $10.50 per brush = $21.00
1 dozen colored pencils x $7.88 per dozen = $7.88
1 sketch book x $16.12 per book = $16.12
Total cost without coupon = $21.00 + $7.88 + $16.12 = $45.00
With the $15.00 off coupon, the total cost becomes:
$45.00 - $15.00 = $30.00
The amount saved by using the coupon is:
$45.00 - $30.00 = $15.00
The percentage saved can be calculated as:
Percentage saved = (Amount saved / Total cost without coupon) x 100%
Percentage saved = ($15.00 / $45.00) x 100%
Percentage saved = 33.33%
Therefore, the customer saved 33.33% by using her coupon.