A, B and C set off from the east and west cities at the same time. A and B travel from the east city to the west city. A walks 5 kilometers per hour, B rides a bicycle 15 kilometers per hour, and C also rides a bicycle 20 kilometers per hour. Kilometers, it is known that after C met B on the way, it took another hour to meet A, how many kilometers is the distance between the east and west cities?
甲、乙和丙同时由东、西两城出发，甲、乙两人由东城到西城，甲步行每小时走5千米，乙骑自行车每小时行15千米，丙也骑自行车每小时20千米，已知丙在途中遇到乙后，又经过1小时才遇到甲，求东、西城相距多少千米？
<gadget id="calculator">15 + 20</gadget>
<output>35</output>

<gadget id="calculator">5 + 20</gadget>
<output>25</output>

<gadget id="calculator">20 - 5 - 20</gadget>
<output>-5</output>

<gadget id="calculator">15 + (-5)</gadget>
<output>10</output>

<gadget id="calculator">25 / 10</gadget>
<output>5/2 = around 2.5</output>

<gadget id="calculator">35 * (5/2)</gadget>
<output>175/2 = around 87.5</output>

<result>175/2 = around 87.5</result>