C :

#include<stdio.h>

int main()
{
    double N,X;
	scanf("%lf",&N);
	if(N<=2000)
	{
	    printf("Isento");
	}
	else if(N>2000&&N<=3000)
	{
		X=(N-2000)*0.08;
	    printf("R$ %.2lf",X);
	}
	else if(N>3000&&N<=4500)
	{
	    X=1000*0.08+(N-3000)*0.18;
		printf("R$ %.2lf",X);
	}
	else
	{
	    X=1000*0.08+1500*0.18+(N-4500)*0.28;
		printf("R$ %.2lf",X);
	}

    return 0;
}

C++ :

#include<cstdio>

using namespace std;

int main()
{
    double a;
  
    scanf("%lf",&a);
    
    if(a<=2000.00)  printf("Isento");
    
    if(a>2000.00&&a<=3000.00)  printf("R$ %.2lf",(a-2000.00)*0.08);
    
    if(a>3000.00&&a<=4500.00)  printf("R$ %.2lf",80+(a-3000.00)*0.18);
    
    if(a>4500.00)  printf("R$ %.2lf",350+(a-4500.00)*0.28);
    
    return 0;
}

Java :

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        double second = 0;
        double third = 0;
        double more = 0;
        Scanner scanner = new Scanner(System.in);
        double wage = scanner.nextDouble();
            if (wage >= 0.00 && wage <= 5000) {
                if (wage >= 2000.01 && wage <= 3000.00) {
                    second = (wage - 2000.00) * 0.08;
                    double all = second + third + more;
                    System.out.println("R$ " + String.format("%.2f", all));
                } else if (wage >= 3000.01 && wage <= 4500.00) {
                    second = 1000 * 0.08;
                    third = (wage - 3000.00) * 0.18;
                    double all = second + third + more;
                    System.out.println("R$ " + String.format("%.2f", all));
                } else if (wage > 4500.00) {
                    second = 1000 * 0.08;
                    third = 1500 * 0.18;
                    more = (wage - 4500.00) * 0.28;
                    double all = second + third + more;
                    System.out.println("R$ " + String.format("%.2f", all));
                } else {
                    System.out.println("Isento");
                }

            }

        }
    }