Mr. Li needs to transfer from A to B by car and train. The speed of the train is 150 km/h, and the speed of the car is half of that of the train. It is known that Mr. Li takes 12 hours by train and 4 hours by car. How many miles is it from A to B?
李先生从甲地到乙地需换乘汽车和火车两种交通工具，火车150千米/时，汽车的速度是火车的一半．已知李先生乘火车12小时，乘汽车4小时．甲地到乙地有多少千米？
<gadget id="calculator">150 * 12</gadget>
<output>1_800</output>

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

<gadget id="calculator">75 * 4</gadget>
<output>300</output>

<gadget id="calculator">1_800 + 300</gadget>
<output>2_100</output>

<result>2_100</result>