Final answer:
There are three paranasal sinuses located in the frontal and sphenoid bones; the frontal bone contains two (one on each side), and the sphenoid bone contains one. The parietal bones do not contain any sinuses.
Step-by-step explanation:
The number of paranasal sinuses located in the frontal, sphenoid, and parietal bones is as follows: The frontal sinus can be divided into two, one in each half of the frontal bone above the eyebrows, making it the most anterior sinus. The sphenoid sinus is a single, midline sinus located in the body of the sphenoid bone, making it the most posterior sinus. However, the parietal bones do not house any sinuses. Therefore, considering the frontal and sphenoid bones only, the number of sinuses is three.