Question

Fe2O3+2Al ~2Fe+Al2O3

Answer 1

I presume that you mean 15.0 g of iron(III) oxide

moles Fe2O3 = 15.0 g /159.694 g/mol= 0.0939

the ratio between Fe2O3 and Al2O3 is 1 : 1

moles Al2O3 = 0.0939

mass Al2O3 = 0.0939 mol x 101.963 g/mol= 9.57 g