The average of the two numbers A and B is 42, and the ratio of A and B is 3:4, so what is the number A?
甲、乙两数的平均数是42，甲、乙两数的比是3：4，那么，甲数是多少．
<gadget id="calculator">3 + 4</gadget>
<output>7</output>

<gadget id="calculator">2 / 7</gadget>
<output>2/7 = around 0.285714</output>

<gadget id="calculator">42 * (2/7)</gadget>
<output>12</output>

<gadget id="calculator">3 * 12</gadget>
<output>36</output>

<result>36</result>