One mole of

units()

contains three times as many sulfur atoms.

So

3 X =
atoms of sulfur.

3.42 grams of

must be converted to moles first,
(divide by its formula mass (342 atomic mass units)).

3.42 grams/342 atomic mass units
= 0.01mole.
So! the number of mole of aluminium atoms is 3 X 0.01 =0.03mole.

So the number of atoms of aluminium is
0.03 X =