Zhang Qiang was sitting on the moving bus, and suddenly found that Li Fang was walking in the opposite direction. The bus arrived at the stop 2 minutes later, and Zhang Qiang got off to chase Li Fang. If Zhang Qiang’s speed was twice that of Li Fang, it would be the speed of the car (1/4), how many minutes will it take for Zhang Qiang to catch up with Li Fang?
张强坐在行驶的公共汽车上，忽然发现李芳正在向相反的方向行走，2分钟后汽车到站，张强下车去追李芳，如果张强的速度是李芳的2倍，是汽车速度的(1/4)，那么张强追上李芳要多少分钟？
<gadget id="calculator">4 / 1</gadget>
<output>4</output>

<gadget id="calculator">2 * 4</gadget>
<output>8</output>

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

<gadget id="calculator">2 + 8 + 2 + 8</gadget>
<output>20</output>

<result>20</result>