A car is driving from city A to city B (with the same speed). At this time, three cars A, B and C in city B start from city B at the same time. The speed of A and B is the same, and the speed of C is twice that of A. In the direction of the city, B and C are in the opposite direction. A travels 20 kilometers and meets the car. After meeting, the car catches up with B after 2 hours, and catches up with C after 2 hours. Find the distance between the two cities of AB?
一辆汽车从A城开往B城(速度不变)，这时B城甲乙丙三辆车同时从B城出发，甲、乙的速度相同，丙的速度是甲的2倍，甲向A城方向，乙丙向相反方向，甲行20千米与汽车相遇，相遇后汽车经过2小时追上乙，又经过2小时追上丙，求AB两城的距离？
<gadget id="calculator">20 + 20</gadget>
<output>40</output>

<gadget id="calculator">40 / 2</gadget>
<output>20</output>

<gadget id="calculator">20 * 2</gadget>
<output>40</output>

<gadget id="calculator">20 + 40</gadget>
<output>60</output>

<gadget id="calculator">2 + 2</gadget>
<output>4</output>

<gadget id="calculator">60 / 4</gadget>
<output>15</output>

<gadget id="calculator">20 - 15</gadget>
<output>5</output>

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

<gadget id="calculator">5 / 1</gadget>
<output>5</output>

<gadget id="calculator">5 + 5 + 20</gadget>
<output>30</output>

<gadget id="calculator">40 / 2 / 5 / 1</gadget>
<output>4</output>

<gadget id="calculator">30 * 4</gadget>
<output>120</output>

<result>120</result>