certain city’s tap water charging regulations: Each household’s monthly water consumption within 10 tons (including 10 tons) is charged at 2.5 yuan per ton, and the excess of 10 tons is charged at 3.5 yuan per ton. Xiaoming’s family paid a total of 63.5 yuan for water in April , How many tons of water did his family use in April?
某市自来水收费规定：每户每月用水10吨以内(含10吨)按2.5元一吨收费，超过10吨的其超出部分按每吨3.5元收费，小明家四月份共交水费63.5元，他家四月份用水多少吨？
<gadget id="calculator">2.5 * 10</gadget>
<output>25</output>

<gadget id="calculator">63.5 - 25</gadget>
<output>38.5</output>

<gadget id="calculator">38.5 / 3.5</gadget>
<output>11</output>

<gadget id="calculator">11 + 10</gadget>
<output>21</output>

<result>21</result>