If a and b are two non-empty sets such that axb = bxa, show that a=b?

To prove that A=B, you need to show that A is a subset of B and that B is a subset of A. There is no need to assume that A≠B. We won't be proving this by contradiction. 
First, let a1∈A. Then for any b1∈B, since A X B ⊆ B X A, there exists a2∈A and b2∈B such that a1=b2 and b1=a2. Since b2∈B and a1=b2, we have that a1∈B. Since a1 was arbitrarily chosen, we have that A ⊆B. 
Second, let b1∈B. Then for any a1∈A, since A X B ⊆ B X A, there exists a2∈A and b2∈B such that b1=a2 and a1=b2. Since a2∈A and b1=a2, we have that b1∈A. Since b1 was arbitrarily chosen, we have that B ⊆A. 

Thus we have shown that A=B.

What are the following algebraic equations. you need to post those if you want the answer

No because if you do the higher number minus the lower number you will get a positive. if you do it the other way around you will get a negative number