Ineed asap i forgot how to do this

I'll do 1 as an example, since I think it's just the method you're missing:


The Sigma just means "add from n=1 to n=4" where the bottom is the lower n and the top number is he highest n you go to.

The first one, i believe, would be correct. all the others have one thing in common, and that's that they have repeating numbers. in the second one, x and y have repeating 6's and 3's, and in the third, x and y have repeating 6's as well. in the last one, there are repeating 3's. the first one has no repeating numbers.