We make use of ratios to solve this question.
moles NaOH = c · V = 0.1923 mmol/mL · 26.66 mL = 5.126718 mmol
moles H2SO4 = 5.126718 mmol NaOH · 1 mmol H2SO4 / 2 mmol NaOH = 2.563359 mmol
Hence
[H2SO4]= n/V = 2.563359 mmol / 42.45 mL = 0.06039 M
The answer to this question is [H2SO4] = 0.06039 M