There are a bunch of digital cards, and the numbers written on them are all multiples of 3 or 4. Among them, the number of cards that are multiples of 3 accounts for 2/3 of the total number of cards, and the number of cards that are multiples of 4 accounts for the total number of cards. The quantity (3/4) is a multiple of 12. There are 15 cards. Then, how many cards are there in this pile.
有一堆数字卡片，上面写的数都是3的倍数或4的倍数，其中是3的倍数的卡片的数量占卡片总数量的(2/3)，是4的倍数的卡片的数量占卡片总数量的(3/4)，是12的倍数的卡片有15张，那么，这堆卡片一共有多少张．
<gadget id="calculator">2 / 3</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">3 / 4</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">(3/4) - 1</gadget>
<output>-1/4 = around -0.25</output>

<gadget id="calculator">(2/3) + (-1/4)</gadget>
<output>5/12 = around 0.416667</output>

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

<result>36</result>