A bag of flour (1/4) is 4kg less than its 30%, how much does this bag of flour weigh?
一袋面粉的(1/4)比它的30%少4kg，这袋面粉重多少千克？
<gadget id="calculator">30 / 100</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">(3/10) - (1/4)</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">4 / (1/20)</gadget>
<output>80</output>

<result>80</result>