解：根据通分的运用，
原式=2/8-2/5+1/4
=2/8+2/8-2/5
=4/8-2/5
=1/2-2/5
=5/10-4/10
=1/10
通分：5/8-2/5+1/4
=(5/8+1/4)-2/5
=(5/8+1x2/4x2)-2/5
=5/8+2/8-2/5
=7/8-2/5
=7x5/8x5-2x8/5x8
=35-16/40
=19/40
先通分一下 分母为40.即25/40-16/40+10/40=19/40
5/8-2/5+1/4
=(25-16+10)/40
=19/40
5/8-2/5+1/4
=5/8+2/8-2/5
=7/8-2/5
=35/40-16/40
=19/40
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