Brother and younger brother commute between cities A and B. The speed ratio between brother and younger brother is 4:3. 30 minutes after the two start from city A at the same time, the younger brother starts running at twice the original speed. City B returns. How many minutes did it take for the two people to meet again after they set off from point A?
兄、弟两人往返于A、B两市之间，兄和弟的速度比为4：3，两人同时由A市出发30分钟后，弟以原速的2倍开始跑，兄正好由B市返回．这两人由A地出发后，经过多少分钟又相遇？
<gadget id="calculator">30 * 4</gadget>
<output>120</output>

<gadget id="calculator">30 * 3</gadget>
<output>90</output>

<gadget id="calculator">120 - 90</gadget>
<output>30</output>

<gadget id="calculator">3 * 2</gadget>
<output>6</output>

<gadget id="calculator">6 + 4</gadget>
<output>10</output>

<gadget id="calculator">30 / 10</gadget>
<output>3</output>

<gadget id="calculator">3 + 30</gadget>
<output>33</output>

<result>33</result>