How many ways can 4 candy bars be chosen from a store that sells 30 candy bars (combination)

Using the combination formula (n!/(r!(n−r)!)), you would get a total of 27,405 combinations.

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.