What is the minimum volume of 2.00 M HCl necessary to neutralize completely the hydroxide in 800.0 mL of 0.3 M NaOH?

Answer 1

mols NaOH = M x L = ?
mols HCl = mols NaOH (look at the coefficients in the balanced equation).
M HCl = mols HCl/L HCl. You know mols ad M, solve for L (convert to mL if you wish).