How to solve HCl+ Mg(OH)2=MgCl2 + H2O
Answers
How to Balance:
Mg(OH)2 + HCl → MgCl2 + H2O
Word equation: Magnesium chloride + Water → Magnesium hydroxide + Hydrochloric acid
Type of Chemical Reaction: For this reaction we have a neutralization reaction.
Balancing Strategies: This is a neutralization reaction, and can also called a double displacement reaction. It's neutralization because we have a base, the magnesium hydroxide, added to an acid, HCl. The products are a salt (MgCl2) and and water.
We can say it's double displacement because the Mg and the H essentially switch places.
To balance a reaction I recommend changing the coefficient in front of the H2O to get an even number of oxygen atoms. That should get you started.
Hint-1
Hint-2
Show Balanced Equation
Essential Resources
For a complete explanation, watch:

When balancing chemical equations our goal is to have the same number of each type of atom on both sides of the equation.
Only change the coefficients (these are the numbers in front substances).

Never change the subscripts (the small numbers after elements).

