а)(14/30+7/30+24/30)12/6-2/6-3/6) 45/30:7/6 45/30*6/7=45/35=45/35=9/7=1 2/7 б)(10/60+6/60+4/60)9/15+5/15-1/4) 20/6014/15-1/4) 20/60:29/60 20/60*60/29=20/29