fraction is divided into (5/7), and the sum of the numerator and denominator of the original fraction is 72. What is the original fraction?
一个分数约分之后是(5/7)，原分数的分子与分母的和是72，则原分数是多少．
<gadget id="calculator">7 + 5</gadget>
<output>12</output>

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

<gadget id="calculator">72 * (5/12)</gadget>
<output>30</output>

<gadget id="calculator">72 - 30</gadget>
<output>42</output>

<gadget id="calculator">(5/12) / 42</gadget>
<output>5/504 = around 0.009921</output>

<gadget id="calculator">72 * (5/504)</gadget>
<output>5/7 = around 0.714286</output>

<result>5/7 = around 0.714286</result>