There are two classes, A and B. Transfer (2/15) of the number of people in class A to class B. At this time, (3/5) of class B is (3/4) of class A. It turns out that the number of people in class A accounts for the total number of people in both classes What fraction of?
甲乙两个班，把甲班人数的(2/15)调入乙班，这时乙班的(3/5)是甲班的(3/4)，问原来甲班人数占两班总人数的几分之几？
<gadget id="calculator">20 + 19</gadget>
<output>39</output>

<gadget id="calculator">20 / 39</gadget>
<output>20/39 = around 0.512821</output>

<result>20/39 = around 0.512821</result>