To answer this question you need to know the equation of both reactions. For every KOH there will be 1 OH- ion, but for every H2SO4 there will be 2 H+ ion. That means one molecule of H2SO4 will neutralize 2 KOH. Then, the amount of H2SO4 needed should be:
250m/350m* 15ml*2= 21.42 ml
