To solve this expression, we need to follow the order of operations (PEMDAS/BODMAS).

First, we need to simplify the fractions within the expression.

6/7.8/13 = (6/7) / (8/13) = (6/7) * (13/8) = 78/56

Next, we can simplify the remaining fractions in the expression.

78/56 + 6/7.9/13.3/13.6/7

To add fractions, we need to find a common denominator. In this case, the common denominator is 56.

78/56 + 6/7.9/13.3/13.6/7 = (78 + 6) / 56 = 84/56

Finally, we can simplify the fraction.

84/56 = 3/2

Therefore, the simplified expression is 3/2.