(1) 6 motorcycles, tricycles and cars are parked in the parking lot, with * * * wheels 15. How many motorcycles, tricycles and cars are there?

4 motorcycles, tricycle 1 car, car 1 car.

(2) Grade four students take part in making paper flowers. Forty-two students made 104 flowers, two boys and three girls. How many boys and girls are there?

42x2=84 (flowers)

104-84=20 (flowers)

Female: 20/(3-2)=20 (person)

Male: 42-20=22 (person)