Astamp collector bought 160 stamps for $25.00. the purchase included 5¢ stamps, 15¢ stamps, and 25¢ stamps. the number of 15¢ stamps is three times the number of 5¢ stamps. how many of each type of stamp was purchased?

5- 30
15- 90
52- 40
Questions?

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.