For a true fraction, the difference between the denominator and the numerator is 12, and the fraction is (5/7). What is the original fraction?
一个真分数，分母与分子的差是12，约分后是(5/7)，原来的分数是多少．
<gadget id="calculator">12 / 2</gadget>
<output>6</output>

<gadget id="calculator">6 * 7</gadget>
<output>42</output>

<gadget id="calculator">5 / 42</gadget>
<output>5/42 = around 0.119048</output>

<gadget id="calculator">6 * (5/42)</gadget>
<output>5/7 = around 0.714286</output>

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