After selling 30% of 4 tons of flour, sell (1/4) tons, how many tons are left.
4吨面粉卖出30%后，又卖出(1/4)吨，还剩多少吨．
<gadget id="calculator">30 / 100</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">1 - (3/10)</gadget>
<output>7/10 = around 0.7</output>

<gadget id="calculator">4 * (7/10)</gadget>
<output>14/5 = around 2.8</output>

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

<gadget id="calculator">(14/5) - (1/4)</gadget>
<output>51/20 = around 2.55</output>

<result>51/20 = around 2.55</result>