Two people, A and B, go from A to B. A walks 4 km per hour on foot, and B rides a bicycle 8 km more than A per hour. B leaves half an hour after A leaves. It happens that both of them arrive at B at the same time. Find both places A and B. the distance between.
甲乙两人从A地去B地，甲步行每小时走4km，乙骑车每小时比甲多走8km，甲出发半小时后乙出发，恰好两人同时到达B地，求A、B两地之间的距离．
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">4 * (1/2)</gadget>
<output>2</output>

<gadget id="calculator">8 - 4</gadget>
<output>4</output>

<gadget id="calculator">4 + 4</gadget>
<output>8</output>

<gadget id="calculator">2 / 8</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">12 * (1/4)</gadget>
<output>3</output>

<result>3</result>