根据要求写出式子或算式.
甲乙两车从两地同时相向而行.甲车每小时行a千米,乙车每小时行b千米,经过5小时两车相遇
(1)用式子表示相遇时,甲车比乙车多行了多少千米?
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(2)用式子表示两地间的路程.
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(3)当a=80,b=75时,甲车比乙车多行了多少千米?
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(4)当a=80,b=75时,两地间的路程是多少千米?
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