For a simple fraction, the sum of the numerator and denominator is 40. If 2 is subtracted from both the numerator and the denominator, the new fraction is (5/7). What is the original fraction?
一个最简分数，分子、分母的和是40，若分子、分母都减去2，得到新的分数为(5/7)，原来的分数是多少．
<gadget id="calculator">40 - 2 - 2</gadget>
<output>36</output>

<gadget id="calculator">5 + 7</gadget>
<output>12</output>

<gadget id="calculator">5 / 12</gadget>
<output>5/12 = around 0.416667</output>

<gadget id="calculator">36 * (5/12)</gadget>
<output>15</output>

<gadget id="calculator">15 + 2</gadget>
<output>17</output>

<gadget id="calculator">40 - 17</gadget>
<output>23</output>

<gadget id="calculator">17 / 23</gadget>
<output>17/23 = around 0.73913</output>

<result>17/23 = around 0.73913</result>