18% of a bag of rice is 31 kg less than its (4/5), how much does this bag of rice weigh?
一袋大米的18%比它的(4/5)少31千克，这袋大米重多少千克．
<gadget id="calculator">4 / 5</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">18 / 100</gadget>
<output>9/50 = around 0.18</output>

<gadget id="calculator">(4/5) - (9/50)</gadget>
<output>31/50 = around 0.62</output>

<gadget id="calculator">31 / (31/50)</gadget>
<output>50</output>

<result>50</result>