There is a fraction. Adding 2 to the numerator equals (3/5), and subtracting 2 from the numerator equals (1/3). Find the original fraction.
有一个分数，分子加上2等于(3/5)，分子减去2等于(1/3)，求原分数．
<gadget id="calculator">3 * 7</gadget>
<output>21</output>

<gadget id="calculator">21 - 6</gadget>
<output>15</output>

<gadget id="calculator">7 / 15</gadget>
<output>7/15 = around 0.466667</output>

<result>7/15 = around 0.466667</result>