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

а) 3/5 + 3/7 + 9/7 * 4/15 = 3/5 + 3/7 + 12/35=
21/35 + 15/35 + 12/35= 48/35 = 1 целая 13/35

б) (7/9 - 1/6) : 2/9 * 21/22= 2 целые 5/8
1) 7/9 - 1/6= 14/18 - 3/18= 11/18
2) 11/18 : 2/9 = 11/18 : 9/2= 11/4
3) 11/4 * 21/22 = 21/8 = 2 целые 5/8