Colin earns $9 an hour working after school at the library. After he recevied his paycheck for the last week, he spent $6 and had $129 left. How many hours did Colin work at the library last week?

129 + 6 = £135
135 (divided) 9 = 15

Therefore Colin worked 15 hours
Hope this helped :)

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.