Fangfang’s family used 11.4 tons of water in April, 1.6 tons more than last month. How many tons did Fangfang’s family use last month?
芳芳家四月份用水11.4吨，比上个月多了1.6吨，芳芳家上个月用水多少吨？
<gadget id="calculator">11.4 - 1.6</gadget>
<output>9.8</output>

<result>9.8</result>