12 prime factors into 2*2*3

so your choices are packets of 1, 2, 4, 6 or 12 and we have options of 1, 2, or 6

12 packets of 1

1 packet of 2, 10 packets of 1

2 packets of 2, 8 packets of 1

3 packets of 2, 6 packets of 1

3 packets of 2, 1 packet of 6

4 packets of 2, 4 packets of 1

5 packets of 2, 2 packets of 1

6 packets of 2

1 packet of 6, 6 packets of 1

1 packet of 6, 1 packet of 2, 4 packets of 1

1 packet of 6, 2 packets of 2, 2 packets of 1

2 packets of 6

there are a dozen different ways to buy a dozen