If a number is added to the least common multiple of 3 and 4, it becomes the common multiple of 2, 3, and 5. What is the smallest number?
一个数加上3和4的最小公倍数后正好成为2、3、5的公倍数，这个数最小是多少．
<gadget id="calculator">2 * 3 * 5</gadget>
<output>30</output>

<gadget id="calculator">3 * 4</gadget>
<output>12</output>

<gadget id="calculator">30 - 12</gadget>
<output>18</output>

<result>18</result>