Answer:
3 stamps
Step-by-step explanation: 42 stamps in equal groups would be 6 stickers/group.
6+3 = 9 stickers in each pile
there was 7 piles so multiply 7 by the 9 stickers in each pile
7· 9 = 63
5 · 12 = 60, so she gave her friends 60 stickers
63-60 = 3