The standard for charging water fees in a certain city is: if the monthly water consumption does not exceed 10 tons, the fee is 1 yuan per ton; if the water exceeds 10 tons, the excess part is charged at 1.8 yuan per ton. In a certain month, Zhang’s family pays 20.8 yuan for water. How many tons of water does Zhang’s family use this month?
某市收取水费的标准是：若每月用水不超过10吨时，每吨收费1元，若超过10吨时，超过部分按每吨1.8元收费．某月，张家交水费20.8元，这个月张家用水多少吨？
<gadget id="calculator">10 * 1</gadget>
<output>10</output>

<gadget id="calculator">20.8 - 10</gadget>
<output>10.8</output>

<gadget id="calculator">10.8 / 1.8</gadget>
<output>6</output>

<gadget id="calculator">6 + 10</gadget>
<output>16</output>

<result>16</result>