Cars A and B set off from Chengdu to Xi'an at the same time. After 15:00, car A lags behind car B by 195 kilometers. It is known that car B travels an average of 78 kilometers per hour, how many kilometers per hour does car A travel on average?
甲乙两车同时从成都出发开往西安．经过15时后，甲车落后乙车195千米．已知乙车平均每时行78千米，甲车平均每时行多少千米？
<gadget id="calculator">195 / 15</gadget>
<output>13</output>

<gadget id="calculator">78 - 13</gadget>
<output>65</output>

<result>65</result>