Question

(a-b) - (b-c) - (c-a)​

Answer 1

$(a - b) - (b - c) - (c - a) \\ a - b - b + c - c +a \\ = - 2b$

Answer 2

(a-b)-(b-c)-(c-a)
a-b-b+c-c+a
= -2b