confused about balancing...

[redXI]

I must be really bad at chemistry, I can't even do these questions...

1. __P + __O2 ---> __P4O10

Answer: 4P+5O2=P4O10

2. __Fe(OH)3 ---> __Fe2O3 + __H2O

3. __Na2CO3 + __ Ca(OH)2 ---> __NaOH + __CaCO3

I can only do number one. As for the rest, I'm completely blank :-X
I need help, in a few days, a big test is waiting to eat me up but I won't lose! That's why. Thanks.