So when you subtract by a negative number, it is the same thing as adding the two numbers.
First find a the LCD, or the least common denominator.
LCM(7,6) = 7•6 = 42
Then make the fractions have 42 as a denominator.
7 5/6 • 7/7 = 7 35/42
4 1/7 • 6/6 = 4 6/42
Finally, add the two mixed numbers
7 35/42
+4 6/42
11 41/42
So 11 41/42 is your answer