Explanation:
In the formula Al2(SO4)3, the subscript outside the parentheses indicates that the entire sulfate group, (SO4), is repeated three times. Within the sulfate group, there is one sulfur atom. Since there are three sulfate groups, we multiply the number of sulfur atoms in one group (1) by the number of repetitions (3).
Therefore, there are 3 sulfur atoms represented in the formula Al2(SO4)3.
