Sally can paint a room in 55 hours while it takes steve 77 hours to paint the same room. how long would it take them to paint the room if they worked together

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.