Answer:
Here is the C++ program:
#include <iostream>  //to use input output functions
using namespace std;   //to identify objects like cin cout
int main(){  //start of main function 
        int MinFloors = 1;  //minimum number of floors 
        int MinRooms  = 10; //minimum number of rooms
        int NoOfFloors;  //stores number of floors
        int NoOfRooms;  //stores number of rooms
        int OccupiedRooms;  //stores number of rooms occupied
        double TotalRooms=0, TotalOccupied=0;   //stores computed total number of rooms and total number of occupied rooms
        cout<<"How many floors does the hotel have? ";  //prompts user to enter number of floors
        do{  //iterates until the user enters valid number of floors
            cout<<"(cannot be less than "<<MinFloors<<"): ";  //error message
            cin >>NoOfFloors;  //reads number of floors from user
        }while(NoOfFloors<MinFloors);  //repeats as long as number of floors is less than minimum number of floors 
        for(int floor=1; floor <= NoOfFloors; floor++){    //iterates through the floors to skip third iteration
            if(floor == 3){   //if floor is third floor
                continue;             }   
            cout<<"How many rooms are on floor "
<<floor;  //prompts user to enter number of floors
            do{  //start of do while loop
                cout<<"(cannot be less than "<<MinRooms<<"): ";  //error message
                cin >>NoOfRooms;  //reads number of rooms from user
            }while(NoOfRooms<MinRooms);    //iterates as long as number of rooms are less than valid minimum number of rooms
            TotalRooms += NoOfRooms;   //adds number of rooms to the count of total number of rooms 
            cout<<"How many of those rooms are occupied?";  //prompts user to enter number of rooms occupied
            do{  //start of do while loop
          cout<<"(cannot be less than 0 or greater than "<<NoOfRooms<<"): ";  //generates error message
          cin >>OccupiedRooms;  //reads number of rooms occupied by user
            }while(OccupiedRooms<0 || OccupiedRooms>NoOfRooms);   //iterates as long as the number of occupied rooms are less than 0 or greater than number of rooms 
            TotalOccupied += OccupiedRooms;    }    //adds number of rooms occupied to the count of total number of occupied rooms    
        cout<<"\nThe hotel has a total of "<<TotalRooms<<" rooms"<<endl;  //displays the total number of rooms in the hotel
        cout<<TotalOccupied<<" are occupied."<<endl;  //displays the total number of occupied rooms
        cout<<(TotalRooms-TotalOccupied)<<" are unoccupied."<<endl;  //displays the total number of unoccupied rooms
cout<<"The occupancy rate is: "<<100*(TotalOccupied/TotalRooms)<<"%"<<endl;     }  //computes and displays the occupancy rate
     
Explanation:
The program first prompts the user to enter number of floors in the hotel. Lets say user enters 6. This is stored in NoOfFloors So
NoOfFloors = 6
So the loop runs for 6 times 
Next it asks user to enter the number of rooms in the floor 1. Lets say user enters 12 so this is stored in NoOfRooms so
NoOfRooms = 12
TotalRooms += NoOfRooms; 
this statement keeps adding number of rooms to TotalRooms so
TotalRooms = 12
Next program asks user about the number of occupied rooms. Lets say user enters 10 so this is stored in OccupiedRooms so
OccupiedRooms = 10
this statement keeps adding number of rooms to TotalOccupied so
  TotalOccupied += OccupiedRooms;
TotalOccupied = 10
At next iteration program asks user again to enter number of rooms in floor 2. Suppose user enters 14 so 
NoOfRooms = 12
TotalRooms += NoOfRooms;
TotalRooms = 12+14
TotalRooms = 26
Program asks again to enter number of occupied rooms so it becomes:
OccupiedRooms = 8
this statement keeps adding number of rooms to TotalOccupied so
  TotalOccupied += OccupiedRooms;
TotalOccupied = 10+8
TotalOccupied = 18
Next is skips floor 3 and iteration 3. and asks user to enter number of rooms in floor 4. Suppose user enters 14
Number of rooms become:
TotalRooms = 12+14+14
TotalRooms = 40
and suppose user enters 14 as occupied rooms so total occupied become:
TotalOccupied = 10+8 + 14
TotalOccupied = 32
For floor 5: Suppose user enters 13
TotalRooms = 12+14+14+13
TotalRooms = 53
For floor 5: Suppose user enters 10
TotalOccupied = 10+8 + 14+10
TotalOccupied = 42
For floor 6: Suppose user enters 12
TotalRooms = 12+14+14+13+12
TotalRooms = 65
For floor 6: Suppose user enters 11
TotalOccupied = 10+8 + 14+10+11
TotalOccupied = 53
Now the loop breaks
Hence
TotalRooms = 65
TotalOccupied  = 53
total unoccupied = TotalRooms-TotalOccupied = 65-53 = 12
The occupancy rate is: 100*(TotalOccupied/TotalRooms) = 100*(53/65) = 81.5385
The output of the program is attached in a screenshot.