Answer:
c = -4
Explanation:
We can tell that c has to be a negative, because the end result is an increased number, and subtracting a negative is adding.
Next, we can tell that -35 and -27 have a difference of -8, so we have to divide -8 by 2.
-8 / 2 = -4
so we know that c = -4
hope this helps :)