The average of the three numbers of A, B, and C is 6, and their ratio is A: B: C = 3: 4: 5, so what is the number of B?
甲、乙、丙的三个数的平均数是6，它们的比是甲：乙：丙=3：4：5，则乙数是多少．
<gadget id="calculator">3 + 4 + 5</gadget>
<output>12</output>

<gadget id="calculator">4 / 12</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">6 * 3 * (1/3)</gadget>
<output>6</output>

<result>6</result>