The vertex form:

The axis of symetry is x = h.

We have

Substitute:

<h3>Answer: x = -3</h3>
The percent discount is 30%.
If you multiply $32 by .30, you will get $9.60. That is the amount of the discount. If you subtract $9.60 from $32, you will get $22.40 which is what he paid before tax. Therefore the percent discount is 30%.
100+16=116 is the right answer