Adding a number to the numerator of a simplest fraction will equal (4/7) after reduction; if subtracting the same number from its numerator, it will be (1/7) after reduction. Find the original simplest fraction.
将一个最简分数的分子加上一个数，约分后就等于(4/7)；如果将它的分子减去同一个数，约分后就得(1/7)．求原来的最简分数．
<gadget id="calculator">4 / 7</gadget>
<output>4/7 = around 0.571429</output>

<gadget id="calculator">1 / 7</gadget>
<output>1/7 = around 0.142857</output>

<gadget id="calculator">(4/7) + (1/7)</gadget>
<output>5/7 = around 0.714286</output>

<gadget id="calculator">(5/7) / 2</gadget>
<output>5/14 = around 0.357143</output>

<result>5/14 = around 0.357143</result>