Divide 30 students into 3 rows on average. If A and B want to stand in adjacent positions in the same row, how many different ways can they stand?
把30位同学平均分成3行．甲、乙两人想站在同一行的相邻位置上，共有多少种不同的站法．
<gadget id="calculator">30 / 3</gadget>
<output>10</output>

<gadget id="calculator">10 - 1</gadget>
<output>9</output>

<gadget id="calculator">9 * 2 * 3</gadget>
<output>54</output>

<result>54</result>