Assuming that they have the necessary amount of straws to match the beads then we can use the following simple equation to solve this problem.
t = b/12 ... where t is the total amount of necklaces and b is the number of beads you have
t = 2700 / 12
225 necklaces.
For 225 necklaces you would also need 1125 straws since each necklace requires 5 straws to be fully made. Therefore if you have this amount you should not run into any problems.
