The distance between A and B is 100 kilometers. There are two people A and B starting from A and going to B. A car starts from A and picks up the two people back and forth. It is known that the speed of the car is 7 times the walking speed of a person. , to arrive in the shortest time, how many kilometers is the walking distance of A?
甲、乙两地相距100千米，有A，B两人从甲地出发，去往乙地，一辆汽车从甲地出发，来回接送这两个人，已知车速是人步行速度的7倍，要在最短的时间内到达，A步行的距离是多少千米？
<gadget id="calculator">7 - 1</gadget>
<output>6</output>

<gadget id="calculator">7 + 1</gadget>
<output>8</output>

<gadget id="calculator">6 / 8</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">6 + 1</gadget>
<output>7</output>

<gadget id="calculator">1 + (3/4) + 7</gadget>
<output>35/4 = around 8.75</output>

<gadget id="calculator">100 / (35/4)</gadget>
<output>80/7 = around 11.428571</output>

<gadget id="calculator">1 + (3/4)</gadget>
<output>7/4 = around 1.75</output>

<gadget id="calculator">(80/7) * (7/4)</gadget>
<output>20</output>

<result>20</result>