The sum of a fraction plus three fractional units is 1; the difference after subtracting one fractional unit is (1/2), what is the fraction.
一个分数加上三个分数单位后和为1；减去一个分数单位后差为(1/2)，这个分数为多少．
<gadget id="calculator">4 / 8</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)</gadget>
<output>5/8 = around 0.625</output>

<result>5/8 = around 0.625</result>