A circle around the lake is 2700 meters. A, B, and C start from the same place and walk around the lake. A and B walk in the same direction, and C walks in the opposite direction. A’s speed is 135 meters per minute, and B’s speed is 90 meters per minute, C's speed is 45 meters per minute. When A and C meet, they immediately turn around and walk in the opposite direction, and soon meet B. How long after departure, A and B meet?
绕湖环行一周是2700米，甲、乙、丙三人从同一地点出发绕湖行走，甲和乙沿同一方向行走，丙沿反方向行走，甲的速度是每分钟135米，乙的速度是每分钟90米，丙的速度是每分钟45米．当甲与丙相遇后，马上转身反向行走，不久与乙相遇．求出发后多长时间，甲与乙相遇？
<gadget id="calculator">135 + 45</gadget>
<output>180</output>

<gadget id="calculator">2_700 / 180</gadget>
<output>15</output>

<gadget id="calculator">135 - 90</gadget>
<output>45</output>

<gadget id="calculator">45 * 15</gadget>
<output>675</output>

<gadget id="calculator">135 + 90</gadget>
<output>225</output>

<gadget id="calculator">675 / 225</gadget>
<output>3</output>

<gadget id="calculator">15 + 3</gadget>
<output>18</output>

<result>18</result>