4分之3+28分之3+70分之3+130分之3+208分之3
=1-1/4+1/4-1/7+1/7-1/10+1/10-1/13+1/13-1/16
=1-1/16
=15/16
要采纳先回答的正确答案.是对答题者劳动的尊重.