Answer:
 A total of 72 passenger planes came in yesterday.
Step-by-step explanation:
 Blue Sky International Airport handles passenger to cargo traffic in a ratio of 8 to 5.
 Number of cargo planes landed yesterday = 45
 Number of passenger planes landed = 
 x Number of cargo planes landed.
 Number of passenger planes landed yesterday = 
 x 45
 = 8 x 9
 = 72 passenger planes.
 So a total of 72 passenger planes came in yesterday.