<s>[INST] Would my method of solving this symmetric difference set be correct and is my answer correct? Problem:  If A = {1, 2, 4, 6, 7} and B = {1, 2, 4, 6} and C = {1, 3, 4, 7}, what is A ⊕ B ⊕ C? 
1) A − B = {1, 2, 4, 6, 7} − {1, 2, 4, 6} = {1, 2, 4, 6, 7} − {1, 2, 4, 6} = {7}
2) B − A = {1, 2, 4, 6} − {1, 2, 4, 6, 7} = {1, 2, 4, 6} − {1, 2, 4, 6, 7} = {} 
3) A ⊕ B = (A − B) ∪ (B − A) = {7} ∪ {} ={7}
4) (A ⊕ B) − C = {7} − {1, 3, 4, 7} = {7} − {1, 3, 4, 7} = {}
5) C − (A ⊕ B) = {1, 3, 4, 7} − {7} = {1, 3, 4, 7} − {7}= {1, 3, 4}
6) (A ⊕ B) ⊕ C = ((A ⊕ B) − C) ∪ (C − (A ⊕ B)) = {} ∪ {1, 3, 4} = {1, 3, 4}
 [/INST] Your answer and working appear to be correct. A noteowrthy fact: for a family of sets $A_1,\cdots,A_n$, we can show that
$$\bigoplus_{i=1}^n A_i = \{ \text{all elements belonging to an odd number of the } A_n \}$$
You can use this fact to quickly verify your answer in a case like this.
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