а) 3/5+3/7+9/7*4/15
б) (7/8-1/6):2/9*21/22

а) 3/5+3/7+9/7*4/15 = 1 13/359/7*4/15 = 12/353/5+3/7+12/35 = 21/35+15/35+12/35= 48/35 = 1 13/35 б) (7/8-1/6):2/9*21/22 = 3 39/1767/8-1/6 = 21/24 - 3/24 = 18/24 = 3/43/4:2/9 = 3/4*9/2=27/827/8*21/22 = 567/176 = 3 39/176