For a fraction, if a number is added to its numerator, the fraction is equal to (5/7); if the same number is subtracted from its numerator, the fraction is equal to (1/2), what is the fraction.
一个分数，在它的分子上加一个数，这个分数就等于(5/7)；如果在它的分子上减去同一个数，这个分数就等于(1/2)，这个分数是多少．
<gadget id="calculator">5 / 7</gadget>
<output>5/7 = around 0.714286</output>

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

<gadget id="calculator">(5/7) + (1/2)</gadget>
<output>17/14 = around 1.214286</output>

<gadget id="calculator">(17/14) / 2</gadget>
<output>17/28 = around 0.607143</output>

<result>17/28 = around 0.607143</result>