Answer:
12 oxygen atoms
Step-by-step explanation:
One formula of Al2(SO3)4 refers to one "molecule" of the given salt.
Now from the given formula, we can note that one formula of the salt has:
2 Al atoms
3 SO4 atoms
Each one of the 3 SO4 atoms has 4 oxygen atoms, therefore:
number of oxygen atoms in one formula of Al2(SO4)3 = 4 * 3 = 12 atoms
Hope this helps :)