Suppose a jar contains 7 red marbles and 21 blue marbles. if you reach in the jar and pull out 2 marbles at random at the same time, find the probability that both are red.

The probability is 1 out of 3 chance.

 this can be answered a couple ways. it could be 7/30 or 21%.

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.