Uncle Wang has to walk 6 kilometers to work every day. Because he got up late one day, he traveled four times as fast as usual for the first half of the journey, and three times as fast for the second half. Use less than 50 minutes, how many meters does Uncle Qiugong usually travel per minute?
王叔叔每天上班要行6千米的路，一天由于起来的较晚，他行前一半的路是平时的4倍，后一半路程的速度是平时的3倍，这样在路上所花时间比原来少用50分钟，求工叔叔平时每分钟行多少米．
<gadget id="calculator">6 * 1_000</gadget>
<output>6_000</output>

<gadget id="calculator">6_000 - 750 - 1_000</gadget>
<output>4_250</output>

<gadget id="calculator">4_250 / 50</gadget>
<output>85</output>

<result>85</result>