It is arithmetical operations but it is logic.
In arithmetic if
A + B so it should be C already.
It should not be the same A (the same value).

Because if we are increasing A on B assigning the result to A so
A will be increasing on B all the time. Every second A will be increasing on B without any stopping. It means A plus B is equal A (the same A?) so plus B once again (because of A plus B) is equal A (an other A) which should be added to B and so on.

May be during the coding everything will be clear.

But I have a question.
In Relational operators A == Bi;
It means true if A equal B else false.

Is it necessary to have i after B?