Hydrogen and oxygen make water
Hydrogen and carbon make methane
Methane and oxygen make water and co2.
Methane and hydrogen don't combine to make anything.
Methane and water make wetfart.

What is needed to make water?
What is combines with oxygen to make water?
Can you make co2 given hydrogen, carbon, and oxygen?

How do you make a rule that says if X+Y makes Z, then Y+X makes Z and not have infinite recursion?

What can be used to make water?  I just want a list of things that help make water.  (i.e. helpmake(X,water).)
   hydrogen combines with oxygen to make water
   oxygen combines with hydrogen to make water
   methane combines with oxygen to make water
   carbon combines with hydrogen to make methane, which combines with oxygen to make water