The route between the two ports is 357 kilometers long. Two ships A and B set off from two ports at the same time, sail towards each other, and meet after 6 hours. Ship A travels 31 kilometers per hour, how many kilometers per hour does boat B travel?
两个港口的航线长357千米．甲乙两艘船同时从两个港口出发，相向而行，经过6小时相遇．甲船每小时行31千米，乙船每小时行多少千米？
<gadget id="calculator">357 / 6</gadget>
<output>119/2 = around 59.5</output>

<gadget id="calculator">(119/2) - 31</gadget>
<output>57/2 = around 28.5</output>

<result>57/2 = around 28.5</result>