Flour is 0.92 yuan per kilogram, and rice is 0.80 yuan per kilogram. If you buy 15 kilograms of flour and 15 kilograms of rice each, and pay 30 yuan, how much should you get back? (two ways to answer)
面粉每千克0.92元，大米每千克0.80元．买面粉和大米各15千克，付出30元，应找回多少元？(两种方法解答)
<gadget id="calculator">0.92 * 15</gadget>
<output>13.8</output>

<gadget id="calculator">0.8 * 15</gadget>
<output>12</output>

<gadget id="calculator">13.8 + 12</gadget>
<output>25.8</output>

<gadget id="calculator">30 - 25.8</gadget>
<output>4.2</output>

<result>4.2</result>