Ken buys gummy vitamins.  They are usually $15.00 per bottle at his grocery store, but they are currently 20% off.  On top of that, he has 3 $2.00 coupons.  How much will 3 bottles cost?
The vitamins are $15.00 a bottle and are currently 20% off so that's 15*.20 = $
<gadget id="calculator">15*.20</gadget>
<output>3</output>
3.00 off.
The vitamins are $15.00 and they are $3.00 off so they are now 15.00-3 = $
<gadget id="calculator">15.00-3</gadget>
<output>12</output>
12.00.
He has 3 $2.00 coupons so that's 3*2 = $
<gadget id="calculator">3*2</gadget>
<output>6</output>
6.00 in coupons.
He buys 3 bottles at $12.00 each so that's 3*12 = $
<gadget id="calculator">3*12</gadget>
<output>36</output>
36.00.
He has $6.00 in coupons so his vitamins will now costs 36-6 = $30.00.

<result>30</result>