Subtraction rules encountered for a DS question

[2amitprakash]

Since the DS question is from official guide, I'm not putting the question in entirety but need to discuss the concept used.
Information in Question: 3 numbers - k, l, m; no other information like k,l,m NE 0 or integers or anything else.
Test condition concept: k-(l+m) can be equal to (k-l)+(k-m) if and only if k=0 but can never be equal for any other value of k - True or False? For me it is True.

[ganeshraj]

K-(l+m) = (K-l)+(K-m)
k-(l+m) = 2K-(l+m)
k=2K

K must be 0.

[RonPurewal]

K-(l+m) = (K-l)+(K-m)
k-(l+m) = 2K-(l+m)
k=2K

K must be 0.

perfect.