Well, when we add a negative number, it's like subtracting.
7 3/5 - 8 4/7
Now, in adding and subtracting, we need a common denominator to be able to add. Remember that anything times 1 is itself, and anything over itself is 1. We are going to multiply each fraction by the denominator of the other over itself (which equals 1).
(3/5)(7/7) = 21/35
(4/7)(5/5) = 20/35
7 21/35 - 8 20/35
Shoot, that's going to be a negative! With terms of different signs, we subtract the terms and use the sign of the term with the biggest absolute value (distance from 0).
8 20/35 - 7 21/35
We can borrow 35/35 from 8...
7 55/35 - 7 21/35 = 34/35
Alrighty, since -8 20/25 has a higher absolute value than 7 21/35, our final answer is...
-34/35
Hope this helps!
