98. Solving a chemistry problem

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