The price of water for residents in a certain place is 3.5 yuan per ton. Xiaofang's family paid a total of 73.50 yuan for water last month. How many tons of water did her family use last month?
某地居民用水的价格是每吨3.5元．小芳家上月一共付水费73.50元，她家上月用水多少吨？
<gadget id="calculator">73.5 / 3.5</gadget>
<output>21</output>

<result>21</result>