Cars A and B start from AB at the same time and drive toward each other. The distance between the two places was 30 kilometers when they met for the first time. After the meeting, they each arrived at the other side and returned immediately. The second meeting was at a distance of 15 kilometers from the midpoint on the side of the midpoint B of the two places. What is the distance between the two places? ?
甲、乙两车同时从AB两地同时出发相向而行．第一次相遇时距离A地30千米，相遇后各自到达对方立即返回，第二次相遇在两地中点B地一侧距离中点15千米处，问两地之间的距离是多少？
<gadget id="calculator">30 * 3</gadget>
<output>90</output>

<gadget id="calculator">90 - 15</gadget>
<output>75</output>

<gadget id="calculator">75 * 2</gadget>
<output>150</output>

<result>150</result>