0,8(8) = 8/9
2х - 0,8(8) = 1 целая 2/3
2х - 8/9 = 5/3
2х = 5/3 + 8/9
2х = 15/9 + 8/9
2х = 23/9
х = 23/9 : 2
х = 23/9 * 1/2
х = 23/18
х = 1 целая 5/18
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Проверка:
2 * 23/18 - 8/9 = 23/9 - 8/9 = 15/9 = 5/3 = 1 целая 2/3