First, we need to convert all the mixed numbers to improper fractions:

7 1/7 = 50/7
2 6/13 =32/13
3 1/7= 22/7

Now we can plug the values back into the equation:

50/7 - (32/13 + 22/7)

Now we need to find a common denominator to combine the fractions:

The common denominator is 91 (7 x 13)

[(50 x 13) - (32 x 7 + 22 x 13)] / 91
[650 - (224 + 286)] / 91
[650 - 510] / 91
140 / 91

So, the final answer is 140/91 or 1 49/91.