A bottle of mineral water is 3 yuan. Xiaohong has 28 yuan, bought 9 bottles of mineral water, how much money is left.
一瓶矿泉水3元．小红有28元钱，买了9瓶矿泉水，还剩多少元．
<gadget id="calculator">3 * 9</gadget>
<output>27</output>

<gadget id="calculator">28 - 27</gadget>
<output>1</output>

<result>1</result>