вычислите:a)3/14+5/21
б)7/8-0,4
в)2/3-(4/7-1/6)

а) 3/14+5/21=9/42+10/42=19/42б)7/8-0.4=7/8-2/5=35/40-16/40=19/40 в)2/3-(4/7-1/6)=2/3-(24/42-7/42)=2/3-17/42=28/42-17/42=3/14