Subtract 3 from the denominator of a fraction, the numerator remains unchanged, and the result is (2/3); if you add 1 to its denominator, the numerator remains unchanged, and the result is (1/2), what is the original fraction ?
一个分数的分母减去3，分子不变，约分后是(2/3)；若将它的分母加上1，分子不变，约分后是(1/2)，求原分数是多少？
<gadget id="calculator">3 + 1</gadget>
<output>4</output>

<gadget id="calculator">2 - 1.5</gadget>
<output>0.5</output>

<gadget id="calculator">4 / 0.5 / 15</gadget>
<output>0.533333</output>

<result>0.533333</result>