Solving a chemistry problem

5. A sample of steel weighing 0.7468 g was dissolved in a flask with a capacity of 50.0 ml. Two samples of 20.00 ml each were placed in flasks with a capacity of 50.0 ml; a solution containing 0.0030000 g of vanadium was added to one flask. Hydrogen peroxide was added to both flasks and brought to the mark. Calculate the mass fraction (%) of vanadium in steel if the following optical densities were obtained during photometry: DX=0.250 and DX+cm=0.530. When deciding to use the graphical method.