First, you had 88/93 and 6/47 parts of a cake. You added these together, then added 92/4 more parts to get a whole new cake. Now consider a slightly different scenario. 

Instead of starting with 88/93 parts of the cake, you only started with 84/93 parts of it, but you still added the same 6/47 and 92/4 parts. How much cake do you have in total now?