Call

It is given that both salts contain the same number of sulfur atoms. Thus we have $Al_2S_3O_12$, and necessarily $3$ $xx$ $H_2SO_4$. There are $3$ $"equiv"$ sulfuric acid per equiv aluminum sufate, and necessarily $"12"$ $"equiv"$ of $O$ atoms in the acid. And (if I have been doing my sums correctly), the ratio of oxygens is $1:1$.

This is a nasty question, which I suspect has been asked below A level.

PS You have just asked a bunch of questions. Do you think that you could spend some time formatting the questions properly? It makes interpreting the question a much easier proposition.