Towns A and B are 120 kilometers apart, and Town C is located between the two towns. There are two means of transportation from town A to town B, and the speed of one means of transport is twice that of the other. Wang Ning and Ma Tao set off from Town A to Town B at the same time at 9:00 am on Sunday. Wang Ning first took the first type of transportation from town A to town C, and then changed to the second type of transportation to arrive at town B at 2:00 p.m. Ma Tao first takes the second means of transportation from town A to town C, and then transfers to the first means of transportation to arrive at town B at 4:00 p.m. Find the speed of the first vehicle.
A、B两镇相距120千米，C镇位于两镇之间．从A镇去B镇有两种交遭工具，一种交通工具的速度是另一种的2倍．周日王宁和马涛两人于上午9：00同时从A镇出发前往B镇．王宁先乘第一种交通工具从A镇到C镇，然后再换乘第二种交通工具于下午2：00到达B镇．马涛先乘第二种交通工具从A镇到C镇，然后再换乘第一种交通工具于下午4：00到达B镇．求第一种交通工具的速度．
<gadget id="calculator">16 - 9</gadget>
<output>7</output>

<gadget id="calculator">14 - 9</gadget>
<output>5</output>

<gadget id="calculator">7 + 5</gadget>
<output>12</output>

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

<gadget id="calculator">12 / 3</gadget>
<output>4</output>

<gadget id="calculator">4 * 2</gadget>
<output>8</output>

<gadget id="calculator">120 / 8</gadget>
<output>15</output>

<result>15</result>