To find the unit rate of beads per bracelet, divide the total number of beads by the number of friends (which represents the number of bracelets).
Total beads = 156
Number of friends = 12
Unit rate of beads per bracelet = Total beads / Number of friends
Unit rate = 156 beads / 12 friends = 13 beads per bracelet
So the answer is 13 beads.