139. Solving a chemistry problem

After dissolving 0.6150 g of steel, the solution was diluted to 50.0 cm3. In two flasks with a capacity of 50.0 cm3, 20.0 cm3 of this solution was placed and added:
in the first flask - a standard solution containing 0.001000 g of Ti, solutions of Н2О2 and Н3РО4, in the second - solutions of Н2О2 and Н3РО4, in the third - a solution of Н3РО4 (reference solution). The solutions were diluted to the mark and the first two solutions were photometrically measured against the third. Received the values of optical density: Ax + st = 0.470, Ax = 0.250. Calculate the mass fraction (%) of titanium in steel.