In order to encourage residents to save water, the water company stipulates that each household uses 2.6 yuan per ton within 10 tons (including 10 tons), 2.8 yuan per ton for 10 to 20 tons, and 3 yuan per ton for more than 20 tons. Guangming Primary School paid 150 yuan for water last month. How many tons of water did Guangming Primary School use last month?
为鼓励居民节约用水，自来水公司规定：每户每月用水10吨以内(含10吨)每吨2.6元，10至20吨每吨2.8元，超过20吨的每吨3元．光明小学上月交水费150元，光明小学上月用水多少吨？
<gadget id="calculator">10 * 2.6</gadget>
<output>26</output>

<gadget id="calculator">20 - 10</gadget>
<output>10</output>

<gadget id="calculator">10 * 2.8</gadget>
<output>28</output>

<gadget id="calculator">150 - 26 - 28</gadget>
<output>96</output>

<gadget id="calculator">96 / 3</gadget>
<output>32</output>

<gadget id="calculator">20 + 32</gadget>
<output>52</output>

<result>52</result>