Supernova A must be further than Supernova B, because the more the distance, the less the brightness appears, and the closer you are, the brighter it seems. If Supernova A is 1/4 as bright as Supernova B, Supernova A must be twice as far away than Supernova B, meaning Supernova B is closer to wherever you are viewing.
A lot of Supernovas in one sentence, but, I hope this helps!
