10 students line up in a row to play the game, every two students are separated by 3 meters, Xiao Ming is in the first place, and Xiao Wei is in the seventh place, how many meters are the distance between them?
10个同学排成一列做游戏，每两个同学间隔3米，小明在第一位，小伟在第七位，他们间隔多少米．
<gadget id="calculator">7 - 1</gadget>
<output>6</output>

<gadget id="calculator">3 * 6</gadget>
<output>18</output>

<result>18</result>