carTrip.c

#include <stdio.h>

/*
You are planning a car trip so you post on a carpooling website in order 
to share the cost of the trip.

If you have 0 passengers the carpool site does not charge anything 
and you alone pay the full cost of the trip. If you have 1 or more 
passengers the carpool site adds a $1 fee to the cost of the trip 
and evenly divides the total cost ($1 fee + gas) among the passengers 
and you. You want to write a program that calculates the cost you 
have to pay. The program should read the number of passengers (an integer) 
and the cost of gas for the trip (a decimal number). The program should 
then print the cost that you have to pay (a decimal number) with 2 digits 
after the decimal point.
*/

int main(void) {
    int numberOfPassengers;
    double costOfGas, amount;
    
    scanf("%d%lf", &numberOfPassengers, &costOfGas);
    if (numberOfPassengers < 1) {
        amount = costOfGas;
    }else {
        amount = (1 + costOfGas) / (1+ numberOfPassengers);
}
    
    printf("%.2lf", amount);
    
    return 0;
}