The chemical formula for the selenous acid is H2SeO3. Its reaction with sodium hydroxide, which has a chemical formula of NaOH, will be a neutralization reaction forming a salt and water. This is depicted below.
H2SeO3 + NaOH à Na2SeO3 + H2O
If we are to balance the chemical reaction then, we will have a final answer of,
H2SeO3 + 2NaOH à Na2SeO3 + 2H2O