But Wang Gang sent books to Li Hong. The distance between the two families was 840 meters. To save time, they set off from home at the same time and met in 7 minutes. Li Hong walks an average of 57 meters per hour, how many meters per minute does Wang Gang walk on average?
王刚却给李红送书，两家相距840米，为节省时间，两人同时从家出发，7分钟相遇．李红平均每小时行57米，王刚平均每分钟行多少米？
<gadget id="calculator">840 / 7</gadget>
<output>120</output>

<gadget id="calculator">120 - 57</gadget>
<output>63</output>

<result>63</result>