To solve this problem, we first need to convert all the mixed numbers into improper fractions.

4 - 1 2/7 = 4 - (7*1 + 2) / 7 = 4 - 9/7 = 28/7 - 9/7 = 19/7

6/7 + 1 1/7 = 6/7 + (7*1 + 1) / 7 = 6/7 + 8/7 = 14/7 = 2

So, the expression becomes:

19/7 - 2

To subtract fractions, we need to have a common denominator, which in this case is 7.

19/7 - 2 = 19/7 - 14/7 = (19 - 14) / 7 = 5/7

Therefore, (4-1 2/7)-(6/7+1 1/7) = 5/7.