There is a river between A and B with a length of 210 km. A boat can go down the river from A to B in 2 hours, but it takes 14 hours to return. What is the speed of the boat in still water in km/h?
A、B两地有一条河流，长210km，一只船从A顺水而下2小时可以到达B地，返回时却用了14个小时，则船在静水中的速度是多少km/h．
<gadget id="calculator">210 / 2</gadget>
<output>105</output>

<gadget id="calculator">210 / 14</gadget>
<output>15</output>

<gadget id="calculator">105 + 15</gadget>
<output>120</output>

<gadget id="calculator">120 / 2</gadget>
<output>60</output>

<result>60</result>