The probability of even a is x, and the probability of even b is y, if the two evens are independent, which of these conditions must be true?

I think you meant to write "event" instead of "even".

P(A) = x

P(B) = y

P(A and B) = P(A)*P(B)

P(A and B) = x*y

you multiply the two probability values. This rule only works because the two events are independent.

yes the total will be same because in both of them the expression.is rearranged but their sign remains the same hence it hss just been shuffled