7-2) How many triangles are there?

7-3) Which fraction is the smallest?

7-4) If A # B = (A x B) / (A + B)

a) Calculate 9 # (10 # 10)

b) Calculate 8 # (5 # 5)

7-5) Max started to read a novel. He read 15 pages a day. After 6 days he had 3/8 of the book left. How many pages are there in the book?