What is the total number of sulfur atoms represented in \(3Ca (SO_4)_3\) ?

Sulfur is indicated by the symbol S and we are required to find the total number. Notice that the subscript 4 is only attached to the O atom so it will not be included in our calculation; however, the subscript 3 outside of the parenthesis will count. The coefficient 3 indicates that there are 3 total molecules, and each of these has 3 atoms of sulfur. Multiply: \(3 \times 3 = 9\)