(2.3\9-1.7\9)+ 6.4\9 -(4.2\9+8\9)
( 2 3/9 - 1 7/9 ) + 6 4/9 - ( 4 2/9 + 8/9 ) =
2 3/9 - 1 7/9 = 21/9 - 16/9 = 5/9
5/9 + 6 4/9 = 5/9 + 58/9 = 63/9 = 7
4 2/9 + 8/9 = 38/9 + 8/9 = 46/9 = 5 1/9
7 - 5 1/9 = 7/1 - 46/9 = 63/9 - 46/9 = 17/9 = 1 8/9
(2.3\9-1.7\9)+ 6.4\9 -(4.2\9+8\9)=1,8/9
1) 2.3\9-1.7\9=5/9
2) 5/9+6,4/9=7
3) 4,2/9+8/9=5,1/9
4) 7-5,1/9=1,8/9