Yisir designs bracelets. he use between 9 and 15 red and yellow beads in a ratio of 2 reds beads to 5 yellow beads. how many red and yellow beads does he use?

If he only uses between 9 and 15, we know the only totals possible: 10, 11, 12, 13, 14.

If the ratio is 2:5 for red:yellow, then if he uses:

1 set it is 2:5 = 7 beads; no since less than 9.
2 sets is 4:10 = 14 beads; yes since between our targets.
3 sets is 6:15 = 21 beads; no since more than 15.