Car A and car B drive from city A to city B at the same speed, car C drives from city B to city A, 15 minutes after car A leaves, car B and car C start again at the same time, as a result, car A and car C meet at At the midpoint of the two cities, B and C meet at a distance of 9 kilometers from the midpoint. When car C arrives at city A, car A is still 15 kilometers away from city B. How many kilometers is the distance between the two cities AB?
甲、乙两车以同样的速度从A城开往B城，丙车从B城开往A城，甲车开出15分钟后，乙车和丙车再同时出发，结果甲、丙相遇在两城中点，乙、丙相遇在距中点9千米的地方，当丙车到达A城时，甲车距离B城还有15千米AB两城相距多少千米？
<gadget id="calculator">15 - 9</gadget>
<output>6</output>

<gadget id="calculator">9 / 6</gadget>
<output>3/2 = around 1.5</output>

<gadget id="calculator">15 / 15</gadget>
<output>1</output>

<gadget id="calculator">(3/2) + 1</gadget>
<output>5/2 = around 2.5</output>

<gadget id="calculator">(3/2) - 1</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">2 / (1/2)</gadget>
<output>4</output>

<gadget id="calculator">(5/2) * 9 * 4</gadget>
<output>90</output>

<result>90</result>