15 friends will want pizza for tea each of them will eat 1/3 of a pizza how many pizzas will you need

You will need five pizzas. You divide 15 by 1/3 and get 5

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.