A barrel full of peanut oil weighs 16 kg in total. After (3/5) of the oil is used up, the weight of the barrel is 8.5 kg. What is the weight of the empty barrel?
一个装满花生油的桶，连桶共重16千克，用去(3/5)的油后，连桶共重8.5千克，那么空桶重多少千克．
<gadget id="calculator">16 - 8.5</gadget>
<output>7.5</output>

<gadget id="calculator">3 / 5</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">7.5 / (3/5)</gadget>
<output>12.5</output>

<gadget id="calculator">16 - 12.5</gadget>
<output>3.5</output>

<result>3.5</result>