A walks to school at a speed of 4 kilometers per hour, and B rides a bicycle to catch up with A from the same place 4 hours later than A. B travels 12 kilometers per hour. How many hours can B catch up with A?
甲以每小时4千米的速度步行去学校，乙比甲晚4小时骑自行车从同一地点出发去追甲，乙每小时行12千米，乙多少小时可追上甲．
<gadget id="calculator">12 - 4</gadget>
<output>8</output>

<gadget id="calculator">4 / 8</gadget>
<output>1/2 = around 0.5</output>

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

<result>2</result>