Answer:
-5/7
Explanation:
A sum implies addition.
5 1/2 = A + 6 3/14
we need to put these as mixed numbers:
5 1/2= 11/2 6 3/14= 87/14
so then we have 5 1/2 = A + 87/14
If we multiply 2*7 then we put both fractions into equal terms:
11/2 * 7/7 = 77/14 (remember 7/7 is equal to one so your not actually changing anything)
then we have 77/14= A + 87/14
The we must isolate A by subtracting 87/14 from both sides -10/14 = A, which can be simplified to -5/7
(I'm calling the unknown number A)