Here it's just complete and balanced the following equation. Here we have lithium oxide reactant with hydrochloric acid. We know that when we're reacting with an acid we're going to create water and a salt.
So here lithium oxide is composed of lithium ion and the oxide ion hydrochloric acid is made-up of H plus ion and chloride ion. The lithium and chlorine chloride will combine together to give us our salt. So lithium chloride its aqueous. The oxide and the hydronium ion H combine to give us our liquid water.
To balance this, we need to put a 2 here so that both sides have two lithiums. But now we have 2 chlorines on the product side, so I put a 2 here. This here would represent our balanced overall equation between the reaction of lithium oxide solid and hydrochloric acid.
Li _ 2 O ( s ) + 2 HCl ( aq ) → 2 LiCl ( aq ) + H _ 2 O ( l )