101. Solving a chemistry problem

From a sample of 1.802 g of aluminum salt, 250 ml of a solution were prepared. 25 ml of this solution, under appropriate conditions, was treated with 25 ml of a 0.1N solution of complexon III (fe=1/2); 15.00 ml of 0.1N solution of zinc sulfate (fe=1/2) was used for back titration. Calculate the mass fraction of aluminum, % in the sample.