а) 5/11 - 3/11 + 7/11 = (5 - 3 + 7) / 11 = 9/11
б) 9 13/19 + (8 18/19 - 3 15/19)= 9 + 8 - 3 + 13/19 - 18/19 + 15/19= 14 + 13 - 18 + 10/19= 9 10/19
в) 10 4/21 - (4 10/21 + 3 19/21)= 10 - 4 - 3 + 4/21 - 10/21 - 19/21= 3 + 4 - 10 - 5/21= -3 5/21
а) 5/11 - 3/11 + 7/11 = (5 - 3 + 7) / 11 = 9/11
б) 9 13/19 + (8 18/19 - 3 15/19)
= 9 + 8 - 3 + 13/19 - 18/19 + 15/19
= 14 + 13 - 18 + 10/19
= 9 10/19
в) 10 4/21 - (4 10/21 + 3 19/21)
= 10 - 4 - 3 + 4/21 - 10/21 - 19/21
= 3 + 4 - 10 - 5/21
= -3 5/21