Which of the following statements are true? Select all that apply.
1. for all real numbers A and B, A+B=B+A
2. for all real numbers A and B, AB=BA
3. for all real numbers A and B, A-B=B-A
4. for all real numbers A, B and C, (A+B) + C = A + (B+C)
5. for all real numbers A, B and C, (A-B) - C = A - (B-C)
6. for all real numbers A, B and C, A(B+C)= AB+AC