Subtract a number from the difference between (1/2) and (1/8) to get (1/8). What is this number?
从(1/2)与(1/8)的差里减去一个数，得(1/8)．这个数是多少？
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 / 8</gadget>
<output>1/8 = around 0.125</output>

<gadget id="calculator">(1/2) - (1/8) - (1/8)</gadget>
<output>1/4 = around 0.25</output>

<result>1/4 = around 0.25</result>