3 clocks -> 24

1 clock -> 24/3=8

1 clock + 2 pumpkins -> 26

2 pumpkins -> 26-8=18

1 pumpkin -> 18/2=9

1 clock + 2 presents -> 30

2 presents -> 30-8=22

1 present -> 22/2=11

3 apples -> 6 

1 apple -> 6/3=2

3 screws + 1 apple -> 41

3 screws -> 41-2=39

1 screw -> 39/3=13

1 screw + 2 stars -> 49

2 stars -> 49-13=36

1 star -> 36/2=18