Xiao Ming stands in front of Xiao Liang, and the two start running in the same direction at the same time. Xiao Ming's speed is 4m/s, and Xiao Liang's speed is 6m/s. After x hours, Xiao Liang catches up with Xiao Ming. When starting, Xiao Ming stands in front of Xiao Liang how much m.
小明站在小亮的前面，两人同时同向起跑，小明的速度为4m/s，小亮的速度为6m/s，经过x小时后小亮追上小明，起跑时小明站在小亮前面多少m．
<gadget id="calculator">6 - 4</gadget>
<output>2</output>

<result>2</result>