30% w/v H2SO4 means 30 g H2SO4 in 100 ml solution.
Mass of H2SO4 = 30 g
Density of H2SO4 = 1.05 g/ml
Volume of H2SO4 = Mass/Density = (30 g)/(1.05g/ml) = 28.57 ml
Volume of solution = 100 ml
Density of solution = 1.5 g/ml
Mass of solution = Volume*Density = (100 ml)*(1.5 g/ml) = 150 g
So,
Hence, %v/w = 19.046 %