Oscar wouldn't look at any of the answers until they had all tried their best to work them out, so that meant that he could join in too.
There are pictures here of the layouts of the matchsticks for the 6 puzzles the bears did, numbered 1 to 6. Here are the instructions for each:
Puzzle 1: Leave just 3 squares by removing 3 matchsticks
Puzzle 2: Leave just 3 squares by removing 5 matchsticks
Puzzle 3: Leave just 2 squares by removing 8 matchsticks
Puzzle 4: Leave just 2 squares by removing 2 matchsticks
Puzzle 5: Leave just 6 squares by removing 8 matchsticks
Puzzle 6: Leave just 3 squares by removing 6 matchsticks
You can find out the answers by clicking here. Promise not to look until you have tried puzzling them out yourselves! Have fun!