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