A glass of milk, the mother drank (1/4), the son drank the rest (1/2), how much of this glass of milk did the son drink.
一杯牛奶，妈妈喝了(1/4)，儿子喝了剩下的(1/2)，儿子喝了这杯牛奶的多少．
<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 - (1/4)</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">(3/4) * (1/2)</gadget>
<output>3/8 = around 0.375</output>

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