A certain city carried out water conservation activities. The water company stipulated that if the monthly water consumption of each household is within 20 tons (including 20 tons), it will be charged at 1.5 yuan per ton, and the part exceeding 20 tons will be charged at 1.8 yuan per ton. The water fee of Xiaohong’s family last month was 37.2 yuan. How many tons did Xiaohong’s family actually use last month?
某市开展节约用水活动，自来水公司规定：每户每月用水量在20吨(包括20吨)以内的，按每吨1.5元收费，超过20吨的部分，按照每吨1.8元收费．小红家上个月的水费是37.2元，小红家上个月实际用水多少吨？
<gadget id="calculator">1.5 * 20</gadget>
<output>30</output>

<gadget id="calculator">37.2 - 30</gadget>
<output>7.2</output>

<gadget id="calculator">7.2 / 1.8</gadget>
<output>4</output>

<gadget id="calculator">4 + 20</gadget>
<output>24</output>

<result>24</result>