Xiao Ming went to the store and bought a pencil case worth 9 yuan, and gave 13 yuan to the clerk's aunt, how much should I get back?
小明到商店去买了一个9元钱的文具盒，给营业员阿姨13元钱，应找回多少钱？
<gadget id="calculator">13 - 9</gadget>
<output>4</output>

<result>4</result>