The carnival has 25 rides
Each ride accomodates 120 people (when full)
Each ride was completelly booked for 4 nights .
Step one, calculate how many people can the carnival accomodate in one night by multiplying the number of people by ride by the number of rides:
120*25= 3000
This means that in one night, the carnival can accomodate 3000 people in all 25 rides.
Step two, multiply the value obtained by the number of nights the carnival will be full:
3000*4=12000
The carnival will expect to accomodate 12000 people for 4 nights with all rides full booked.