The average of the three numbers A, B, and two is 15, and the ratio of the three numbers A, B, and C is 2:3:4. What is A's number?
甲、乙、两三个数的平均数是15，甲、乙、丙三个数的比是2：3：4，甲数是多少．
<gadget id="calculator">2 + 3 + 4</gadget>
<output>9</output>

<gadget id="calculator">2 / 9</gadget>
<output>2/9 = around 0.222222</output>

<gadget id="calculator">15 * 3 * (2/9)</gadget>
<output>10</output>

<result>10</result>