The average of the three numbers A, B, and C is 105, the ratio of A and B is 2:3, and the ratio of B and C is 4:5. So what is the number B?
甲、乙、丙三个数的平均数是105，甲、乙两数比是2：3，乙、丙两数比是4：5．那么乙数是多少．
<gadget id="calculator">105 * 3</gadget>
<output>315</output>

<gadget id="calculator">8 + 12 + 15</gadget>
<output>35</output>

<gadget id="calculator">12 / 35</gadget>
<output>12/35 = around 0.342857</output>

<gadget id="calculator">315 * (12/35)</gadget>
<output>108</output>

<result>108</result>