Answer:
// class definition of MethodPractice
public class MethodPractice {
    // main method that begin program execution
    public static void main(String args[]) {
        // call to the planParty2 method is done using some parameter
        // and the return value is displayed
      System.out.println("The number of p-packs needed is: " + planParty2(9, 14, 6));
      System.out.println("The number of p-packs needed is: " + planParty2(4, 6, 3));
      System.out.println("The number of p-packs needed is: " + planParty2(4, 6, 4));
    }
    
    // planParty2 method with 3 parameters and it return an integer
    // the calculation needed to get the required pack is done here
    public static int planParty2(int f, int c, int p){
        // the party owner is added to list of friend
        // and the value is assigned to totalPeople
        int totalPeople = f + 1;
        // the totalPeople times the can drink 
        // is assigned to totalDrinkNeeded
        int totalDrinkNeeded = totalPeople * c;
        // number of packs required is declared
        int numberOfPacks;
        // if the totalDrinkNeeded contains exact multiple of a pack
        // we return the numberOfPack by dividing totalDrinkNeeded with p
        if (totalDrinkNeeded % p == 0){
            return numberOfPacks = totalDrinkNeeded / p;
        } 
        // else we compute if the totalDrinkNeeded is not a multiple of a pack
        //  first we get the remainder when the totalDrinkNeeded is divided with p
        // then the needed can is computed by subtracting remainder from p
        // the neededCan is added to totalDrinkNeeded, then divided with p
        // and assigned to numberOfPacks
        // numberOfPacks is returned.
        else {
            int remainder = totalDrinkNeeded % p;
            int neededCan = p - remainder;
            numberOfPacks = (totalDrinkNeeded + neededCan) / p;
            return numberOfPacks;
        }
    }
}
Explanation:
Image showing the detailed question is attached.
The program is written in Java and is well commented. A sample image of program output when it is executed is attached.