What volume of 0.5M H2SO4 will exactly neutralise 20cm3 of 0.1MNaOH solution?

H2SO4 + 2NaOH ==> 2H2O + Na2SO4

mols NaOH = M x L = ?
Using the coefficients in the balanced equation, convert mols NaOH to mols H2SO4.
Then M H2SO4 = mols H2SO4/L H2SO4. You know mols ad M, solve for L. Convert to cm^3 if needed.