At a high school level, I think you may be able to get away just with considering what hydrolysis means, and writing an equation of the form
Sodium + water -> sodium hydroxide and hydrogen.
Depending on how far you are along in "high school" this could perhaps be balanced as well. I assume you mean lact
ose, not lact
ase, be careful with the vowels, as these are two different beasts.
As to the second part, consider what the galactosidase is doing? Is it being consumed, changed in any way? I don't think (in my opinion) you need to go into the detail as per
http://en.wikipedia.org/wiki/Galactose#Liver_galactose_metabolism at this level.