- Muscles push / pull bones to move the bones
- The muscular system contains muscles
- Hence, the muscular system push / pull bones to move the bones

- The muscular system push / pull bones to move the bones
- Skeletal system is made of bones
- Hence, the muscular system push / pull parts of the skeletal system to move the skeletal system

- Moving parts of something helps to move that something
- A skeletal system is a part of an animal
- Therefore, moving an animal's skeletal system helps to move that animal

- The muscular system push / pull parts of the skeletal system to move the skeletal system
- Moving an animal's skeletal system helps to move that animal
- Therefore, the muscular system moves the skeletal system to help an animal move

- The muscular system moves the skeletal system to help an animal move
- If things are used in a process, then those things are involved in that process
- Hence, the muscular system and the skeletal system are involved in helping an animal move

Therefore, the muscular system and the skeletal system are involved in helping an animal move
Q: Which two body systems are directly involved in movement?
Context:
- Moving parts of something helps to move that something 
- Muscles push / pull bones to move the bones 
- The muscular system contains muscles 
- If things are used in a process, then those things are involved in that process 
- Skeletal system is made of bones 
- A skeletal system is a part of an animal