Java if else statement error WhatsYourGrade

would someone mind helping me figure out how to correctly write my if-else statements? The code is supposed to skip to the next question if the user doesn't enter yes. For example, if they know their Exam 1 score but don't know their exam 2 score it should ask if they know their lab average. If they don't know they're lab average, it should ask do you know your project average?

 import java.util.Scanner;

    public class WhatsYourGrade {

    public static void main(String[] args) {
        // TODO Auto-generated method stub

        System.out.println("Grading Scale:");
        System.out.println("A\t90 - 100");
        System.out.println("B\t80 - 89");
        System.out.println("C\t70 - 79");
        System.out.println("D\t60 - 69");
        System.out.println("F\tbelow 60");

        String letterGrade =  "A , B , C , D , F";

        Scanner keyboard = new Scanner(System.in);
        System.out.print("What letter grade do you want to achieve for the course? ");
        letterGrade = keyboard.next();

        System.out.println("Enter Percentage Weights:");

        int examOne;
        System.out.print("Exam 1:\t");
        examOne = keyboard.nextInt();

        int examTwo;
        System.out.print("Exam 2:\t");
        examTwo = keyboard.nextInt();

        int finalExam;
        System.out.print("Final Exam:\t");
        finalExam = keyboard.nextInt();

        int labs;
        System.out.print("Labs:\t");
        labs = keyboard.nextInt();

        int projects;
        System.out.print("Projects:\t");
        projects = keyboard.nextInt();

        int attendance;
        System.out.print("Attendance:\t");
        attendance = keyboard.nextInt();

        int quizzes;
        System.out.print("Quizzes:\t");
        quizzes = keyboard.nextInt();

        int weights;
        weights = (examOne + examTwo + finalExam + labs + projects + attendance + quizzes);

        if ((weights > 100 ) || (weights < 100)) {
            System.out.print("Weights don't add up to 100, program exiting...");
        }
        else {
            System.out.println("Enter your scores out a 100:");
            System.out.print("Do you know your Exam 1 score? " );

        }
            String score = keyboard.next();

        if ((score.equalsIgnoreCase("Y")) || (score.equalsIgnoreCase("Yes")))   {
            String score1; 
            System.out.print("Score received on exam 1: ");
            score1 = keyboard.next();   
            System.out.print("Do you know your Exam 2 score? ");
        }

            String score2 = keyboard.next();

        if ((score2.equalsIgnoreCase("Y")) || (score2.equalsIgnoreCase("Yes"))) {
            String score3;
            System.out.print("Score received on exam 2: ");
            score3 = keyboard.next();
            System.out.print("Do you know your Final Exam score? ");
        }

            String score4 = keyboard.next();

        if ((score4.equalsIgnoreCase("Y")) || (score4.equalsIgnoreCase("Yes"))) {
            String score5;
            System.out.print("Score received on final exam: ");
            score5 = keyboard.next();
            System.out.print("Do you know your lab average? ");
            String labAverage = keyboard.next();
        }

        else {
            System.out.print("Do you know your lab average? ");
        }
            String labAverage = keyboard.next();

         if ((labAverage.equalsIgnoreCase("Y")) || (labAverage.equalsIgnoreCase("Yes"))) {
            System.out.print("Average Lab Grade: ");
            //String labAvg;
            labAverage = keyboard.next();
        }
            else {
                System.out.print("Do you know your project average?");              
                }
                    String projectAverage = keyboard.next();

                    if ((projectAverage.equalsIgnoreCase("Y")) || (projectAverage.equalsIgnoreCase("Yes"))) {
                    System.out.print("Average Project Grade: ");
                    String projectAvg;
                    projectAverage = keyboard.next();
        }
                    else {
                        System.out.print("Do you know your attendance average?");
                    }

                    String attendAverage = keyboard.next();

                        if ((attendAverage.equalsIgnoreCase("Y")) || (attendAverage.equalsIgnoreCase("Yes"))) {
                            System.out.print("Average Attendance Grade: ");
                        }                       
            keyboard.close();
            }
}