A two-digit number that is not only a multiple of 5 but also divisible by 3 and is an even number, what is the smallest number.
一个两位数，它既是5的倍数，又能被3整除，而且是偶数，这个数最小是多少．
<gadget id="calculator">3 * 5</gadget>
<output>15</output>

<gadget id="calculator">15 * 2</gadget>
<output>30</output>

<result>30</result>