Пошаговое объяснение:

а)

3 8/9 - х = 1 5/9,

х = 3 8/9 - 1 5/9,

х = (3 - 1) + (8/9 - 5/9),

х = 2 + 3/9,

х = 2  3/9,

б)

(у - 8 12/19) + 1 17/19 = 6 2/19,

у - 8 12/19 = 6 2/19 - 1 17/19,

у - 8 12/19 = 5 21/19 - 1 17/19,

у - 8 12/19 = (5 - 1) + (21/19 - 17/19),

у - 8 12/19 = 4 + 4/19,

у - 8 12/19 = 4 4/19,

у = 4 4/19 + 8 12/19,

у = (4 + 8) + (4/19 + 12/19),

у = 12 + 16/19,

у = 12 16/19