The given condition is pretty strange.
Is a/b = odd?
1) a-b = even
2) a+b = even
Consider a = 0 and b = 0, which is not restricted.
1) 0 - 0 = 0 insuff becuase 0/0 = not possible
2) 0 + 0 = 0 insuff becuase 0/0 = not possible
If we were given parameters, for example, a and b does not = 0 then
is a/b = odd? there is only one way for a/b to be definitely odd and that's if both a and b are odd.
consider the following properties:
even - even = even
even - odd = odd
odd - odd = even
odd - even = odd
even + even = even
even + odd = odd
odd + odd = even
odd + even = odd
1) a - b = even
a - b can be even - even or odd - odd, insufficient
2) a + b = even
a + b can be even + even or odd + odd, insufficient
combined, a and b can be both even or both odd, still insufficient.
because a/b = odd can only be answered if we know both a or b are definitely both odd. (one more condition should be added here and that is a/b = integer, for example, if a = 7, b = 5, even if both numbers fit properties 1 and 2, 7/5 is neither even nor odd. It's not an integer)
if they are both even, they can possibly be odd (6/2 = 3) or even (8/4 = 2).
So combined they are insufficient.
E