Xiaohua bought 5 pairs of socks at 6.5 yuan each, and paid 40 yuan. How much should I get back?
小华买了5双袜子，每双6.5元，付了40元，应找回多少元？
<gadget id="calculator">6.5 * 5</gadget>
<output>32.5</output>

<gadget id="calculator">40 - 32.5</gadget>
<output>7.5</output>

<result>7.5</result>