Let us say there are two natural numbers "L" and "R".

We performed eight operations on these two numbers as

Step-1: L = R

Step-2: L x L = R x L

Step-3: L^2 - R^2 = LR - R^2

Step-4: (L + R)( L - R) = R(L - R)

Step-5: L + R = R

Step-6: R + R = R

Step-7: 2R = R

Step- 8: 2 = 1

What is wrong here?

Step5 is Wrong.

We divided the two sides by (L-R).Since L = R which indicates that (L - R) = 0 and we cannot divide by zero.