A gas company adopts the method of billing by monthly segment charges. 2 yuan per cubic meter below 12 cubic meters, 2.5 yuan per cubic meter for the part exceeding 12 cubic meters, Xiaohong’s family used 23 cubic meters of gas last month, how much gas fee do they have to pay?
某燃气公司采用按月分段收费的方法计费．12立方米以下每立方米2元，超过12立方米的部分，每立方米2.5元，小红家上月用燃气23立方米，要付多少燃气费？
<gadget id="calculator">2 * 12</gadget>
<output>24</output>

<gadget id="calculator">23 - 12</gadget>
<output>11</output>

<gadget id="calculator">2.5 * 11</gadget>
<output>27.5</output>

<gadget id="calculator">24 + 27.5</gadget>
<output>51.5</output>

<result>51.5</result>