The ratio of the two numbers of A and B is 3:5, and the difference between the two numbers is 12. What is the number of B?
甲乙两数的比是3：5，两数的差是12，乙数是多少．
<gadget id="calculator">5 - 3</gadget>
<output>2</output>

<gadget id="calculator">12 / 2</gadget>
<output>6</output>

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

<result>30</result>