The number of A is 18, the ratio of A and B is 3:5, what is the number of B?
甲数是18，甲、乙两数的比是3：5，乙数是多少．
<gadget id="calculator">18 / 3</gadget>
<output>6</output>

<gadget id="calculator">6 * 5</gadget>
<output>30</output>

<result>30</result>