原式=5/30+1/30+1/70+1/126+1/198
=1/5+1/70+1/126+1/198
=14/70+1/70+1/126+1/198
=3/14+1/126+1/198
=27/126+1/126+1/198
=2/9+1/198
=44/198+1/198
=5/22