Answer:
20 Animals on each sheets.
Step-by-step explanation:
If there are 20 animals on each sheet, and before he gave 4 sheets away, the total would be 120 animal stickers total.
4 Sheets total have 80 animal stickers
120-80=40
2 sheets = 40 Animal stickers
Divide everything by two
1 Sheet = 20 Animal stickers