The price of a jeans was reduced $6 per week for 7 weeks. by how much did the price of the jeans change over the 7 weeks?

It was reduced by $42.00 by the end of the seven weeks. 

6•7=42, so the price changed $42 in 7 weeks.

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.