(подробно) x+2 1/3+3 1/9-1 1/12=5 7/12

х + 2 1/3 + 3 1/9 - 1 1/12 = 5 7/12

х = 5 7/12 - 2 1/3 - 3 1/9 + 1 1/12

х = (5 7/12 + 1 1/12) - ( 2 1/3 + 3 1/9)

х = 6 8/12 - ( 2 3/9 + 3 1/9)

х = 6 8/12 - 5 4/9 = 6 - 5 + (8/12 - 4/9) = 1 + (24/36 - 16/36) = 1 + 8/36 = 1 2/9

х = 1 2/9