Balance each of the following redox reactions and classify it as a combination, decomposition or displacement reaction.

a) Mg(s)+H2O(g)->Mg(OH)2(s)+H2
b) Cr(NO3)(aq)+Al(s)->Al(NO3)(aq)+Cr(s)
c) PF3(g)+F2(g)->PF5(g)

2 answers

a) Mg + 2H2O ==> Mg(OH)2 + 2H2
single replacement/displacement
What do you not understand about this. It seems simple enough. I shall be happy to explain anything you don't understand.
I know how to balance, I have no idea what the heck any of the classifications are