first we find the moles of H+ and OH- released.
n(HNO3) = 0.030 x 0.1 = 3x10^-3 moles
since HNO3 ionises to produce one H+ ions per molecule, then 3x10^-3 moles of H+ are present
n(Ba(OH)2) = 0.010x0.1 = 1x10^-3 moles
since Ba(OH)2 ionises to produce two OH- ions per molcule, then 2x1x10^-3 =...