Xiao Ming took 20 yuan to the supermarket to buy stationery, and spent 13.5 yuan. How much money does Xiao Ming have?
小明带了20元钱去超市买文具，用去了13.5元，小明还有多少钱？
<gadget id="calculator">20 - 13.5</gadget>
<output>6.5</output>

<result>6.5</result>