Hey there!
Assuming you want this equation balanced:
Ca + H₂O → Ca(OH)₂ + H₂
Balance hydrogen.
2 on the left, 4 on the right. Add a coefficient of 2 in front of H₂O.
Ca + 2H₂O → Ca(OH)₂ + H₂
Balance oxygen.
2 on the left, 2 on the right. Already balanced.
Balance calcium.
1 on the left, 1 on the right. Already balanced.
Our final balanced equation:
Ca + 2H₂O → Ca(OH)₂ + H₂
Hope this helps!