what is the percentage by mass of sulphur in aluminium tetraoxosulphate(VI), Al2(SO4)3

Answer 1

By the way, aluminium tetraoxosulphate(VI) is not an approved IUPAC name for Al2(SO4)3 but aluminium sulphate is.
molar mass = mm = 2*Al + 3*96 = ?
mass S in Al2(SO4)3 is 1 mol S or 32 g S per mol Al2(SO4)3.
%S = [32/mm Al2(SO4)3]*100 = ?