In this case, we'll have to carry out several steps to find the solution.
Step 01:
Data
scrapbooking club = 15%
cooking club = 45%
board game club = ?
Step 02:
board game club = 100 - 15 - 45 = 40%
scrapbooking club:
fraction form = 15 / 100
decimal form = 0.15
cooking club:
fraction form = 45 / 100
decimal form = 0.45
board game club:
fraction form = 40 / 100
decimal form = 0.40
The full solution is:
scrapbooking club:
fraction form = 15 / 100
decimal form = 0.15
cooking club:
fraction form = 45 / 100
decimal form = 0.45
board game club:
fraction form = 40 / 100
decimal form = 0.40