Lainey bought a set of 20 markers for $6

It would be 20 x 6 because 20 sets pf markers for 6 dollars each.

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.