There are several cards, and each card is written with a number, which is a multiple of 3 or a multiple of 4. Among them, cards marked with multiples of 3 occupy (2/3), and cards marked with multiples of 4 occupy (3/4 ). There are 15 cards marked with multiples of 12. So how many cards are there in total? How many
有若干卡片，每张卡片写着一个数，它是3的倍数或是4的倍数，其中标有3的倍数的卡片占有(2/3)，标有4的倍数的卡片占有(3/4)．标有12的倍数的卡片占有15张．那么这些卡片一共有多少张？多少
<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>