Xiaowei rode from the museum to the Railway Bureau at a speed of 12 kilometers per hour. When he set off, two No. 4 trams came from different directions, and they both passed him. When he arrived at the Railway Bureau, they drove behind him. The third oncoming car and the seventh oncoming tram pass him at the same time. All these trams have the same speed and the distance between the two adjacent cars. What is the speed of the tram?
小伟以每小时12千米的速度从博物馆骑车去铁路局，出发时两辆4路电车从不同方向驶来，都恰好从他的身边驶过，当他到铁路局时，从身后驶来的第三辆车和迎面驶来的第七辆电车恰好同时从他身边驶过，所有这些电车的速度及相邻两车之间的距离都相等，那么电车的速度是多少？
<gadget id="calculator">3 * 12</gadget>
<output>36</output>

<gadget id="calculator">12 + 36</gadget>
<output>48</output>

<gadget id="calculator">3 - 1</gadget>
<output>2</output>

<gadget id="calculator">48 / 2</gadget>
<output>24</output>

<result>24</result>