Sara goes shopping with $100 at the mall and she used th
calculate the amount of change she should receive. How
the end of the day?
100 - (12 + 17 + 7 + 2(4) + 3(5) + 4)
$37
$0
$42
$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.