Apples are 3 yuan per kilogram, and oranges are 2.2 yuan per kilogram. Xiao Ming bought 5 kilograms of apples and oranges for 30 yuan, how much should he get back?
苹果每千克3元，桔子每千克2.2元，小明用30元钱买分别买5千克苹果和桔子，应找回多少元？
<gadget id="calculator">3 * 5</gadget>
<output>15</output>

<gadget id="calculator">2.2 * 5</gadget>
<output>11</output>

<gadget id="calculator">15 + 11</gadget>
<output>26</output>

<gadget id="calculator">30 - 26</gadget>
<output>4</output>

<result>4</result>