How do i balance na + h2o = naoh + h2

You have to combine each element on each side together.

You would do

1-Na-1 because there is 1 Na on each side

2-H-3 because there is 2 H on one side and 3 H on the other side

1-O-1 because 1 O on one side and 1 O on the other

Your final answer would be 2Na+2H2O-->2NaOH+H2

Hope I could help! :)