A barrel of oil, use up all (1/4) for the first time, and use up all (3/8) for the second time, what fraction is left?
一桶油，第一次用去全部的(1/4)，第二次用去全部的(3/8)，还剩下几分之几？
<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">3 / 8</gadget>
<output>3/8 = around 0.375</output>

<gadget id="calculator">1 - (1/4) - (3/8)</gadget>
<output>3/8 = around 0.375</output>

<result>3/8 = around 0.375</result>