The speed of the train is increased to 168 kilometers per hour, which is 6 kilometers more than twice the speed before the speed increase. How many kilometers per hour did the train travel before the speed increase? (column equation solution)
火车提速每小时行驶168千米，比提速前的速度的2倍还多6千米，提速前火车每小时行多少千米？(列方程解答)
<gadget id="calculator">168 - 6</gadget>
<output>162</output>

<gadget id="calculator">162 / 2</gadget>
<output>81</output>

<result>81</result>