An express train and a slow train travel from city A to city B at the same time. It is known that the express train takes 8 hours and the slow train takes 10 hours to complete the journey. After the express train arrives in city B, it returns immediately and how many hours later it will meet the slow train.
一列快车和一列慢车同时从甲城开往乙城，已知行完全程快车需要8小时，慢车需要10小时，快车到达乙城后立即返回，再经过多少小时与慢车相遇．
<gadget id="calculator">1 / 10</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">(1/10) * 8</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">1 - (4/5)</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 / 8</gadget>
<output>1/8 = around 0.125</output>

<gadget id="calculator">(1/10) + (1/8)</gadget>
<output>9/40 = around 0.225</output>

<gadget id="calculator">(1/5) / (9/40)</gadget>
<output>8/9 = around 0.888889</output>

<result>8/9 = around 0.888889</result>