3又14/15-1又7/10-3/20=59/15-17/10-3/20=236/60-102/60-9/60=(236-102-9)/60=125/60=25/122又2/7+（1又3/14-0.5）=16/7+17/14-1/2=32/14-17/14-7/14=(32-17-7)/14=8/14=4/7