9 yuan per kilogram of apples, mother bought 4 kilograms, and paid 50 yuan to the salesperson, how much should I get back?
每千克苹果9元，妈妈买了4千克，付给售货员50员，应找回多少元？
<gadget id="calculator">9 * 4</gadget>
<output>36</output>

<gadget id="calculator">50 - 36</gadget>
<output>14</output>

<result>14</result>