An express train and a slow train depart from places A and B at the same time and meet each other after 5 hours. The express train travels 120 kilometers per hour. If the express train leaves first for 3 hours, the two cars can meet each other in 3 hours. Find how many hours it takes for the slow train to travel from point B to point A.
一列快车和一列慢车分别从甲乙两地同时相对开出，经过5小时相遇．快车每小时行120千米，若快车先出发3小时，两车3小时可以相遇．求慢车从乙地到甲地需要多少小时．
<gadget id="calculator">120 * 3</gadget>
<output>360</output>

<gadget id="calculator">120 * 5</gadget>
<output>600</output>

<gadget id="calculator">360 - 600</gadget>
<output>-240</output>

<gadget id="calculator">360 + (-240)</gadget>
<output>120</output>

<gadget id="calculator">5 - 3</gadget>
<output>2</output>

<gadget id="calculator">120 / 2</gadget>
<output>60</output>

<gadget id="calculator">120 + 60</gadget>
<output>180</output>

<gadget id="calculator">5 / 60</gadget>
<output>1/12 = around 0.083333</output>

<gadget id="calculator">180 * (1/12)</gadget>
<output>15</output>

<result>15</result>