Пошаговое объяснение:

1)

4 - 2 8/15 = 3 15/15 - 2 8/15 = 1 7/15,

3 5/9 + 4 11/18  = 3 10/18 + 4 11/18 = 7 21/18 = 8 3/18 = 8 1/6,

2)

( x - 5 3/4) * 2 + 9 7/11 = 12,

(х - 5 3/4) * 2 = 12 - 9 7/11,

(х - 5 3/4) * 2 = 11 11/11 - 9 7/11,

(х - 5 3/4) * 2 = 2 4/11,

х - 5 3/4 = 2 4/11 : 2,

х - 5 3/4 = 26/11 * 1/2,

х - 5 3/4 = 26/22,

х = 26/22 + 5 3/4,

х = 26/22 + 23/4,

х = 52/44 + 253/44,

х = 305/44,

х = 6 41/44