Can some one please explain to me how to easily solve a chemistry equation like 2 HCl + 2 Na?

Step 1: You have to know the type of reaction that occurs. Sodium is a reactive metal and hydrochloric acid is a strong acid, i.e.
Reactive metal + acid → salt + hydrogen
Write the word equation (this can be in your mind) as:
Na + HCl → NaCl + H₂

Step 2: Balance the equation.
2Na + 2HCl → 2NaCl + H₂

Sodium + Hydrochloric Acid = Sodium Chloride and Hydrogen .
Na + HCl = NaCl + H
Since hydrogen (H) exists as a diatomic molecule it must be written as 'H2'
Hence the above eq'n required two hydrogens in the reactant.
HCl becomes 2HCl ( HCl & Another HCl)
This leaves us with two chlorines to accommodate. and the are reacted with two separate atoms of sodium (Na)
Hence the BALANCED reaction is
2Na(s) + 2HCl(aq) = 2NaCl(aq) + H2(g)

The Law of Conservation of Mass applies. The masses on both sides must sum to the same total.. Thereby the number and type of each atom MUST balance.
Casually you can pick up the pack , shuffle it around , but you cannot 'magic' up or 'loose' atoms.

2+2=4