If the average number of A, B, and C is 27, and their ratio is 2:3:4, then what is A?
若甲、乙、丙的平均数是27，它们的比是2：3：4，则甲是多少．
<gadget id="calculator">27 * 3</gadget>
<output>81</output>

<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">81 * (2/9)</gadget>
<output>18</output>

<result>18</result>