39/78=1/2,100/120=5/6,77/99=7/9,45/120=3/8,21/28=3/4,12/27=4/9,25/60=5/12,350/800=7/16
分别是1/2,5/6,7/9,3/8,3/4,4/7,5/12,7/16
