Thanks that question was really bugging me.
I have another question relating to objects.
Design a class named LinearEquation for a 2 x 2 system of linear equations.
The class contains:
private data fields a, b, c, d, e, f
A constructor with the arguments a, b, c, d, e, f
getters & setters for all private data fields
A getX() method and getY() method that return solution for equation.
getX() and getY() methods are always returning 0.0 no matter what I input. Here's my code

public class LinearEquation {
	private double a;
	private double b;
	private double c;
	private double d;
	private double e;
	private double f;
	private double x;
	private double y;
	
	public LinearEquation(double ab, double bc, double cd, double de, double ef, double fg){
		setA(ab);
		setB(bc);
		setC(cd);
		setD(de);
		setE(ef);
		setF(fg);
		
	}
	
	public void setA(double first) {
		this.a = first;
	}
	
	public double getA() {
		return this.a;
	}
	
	public void setB(double second){
		this.b = second;
	}
	
	public double getB() {
		return this.b;
	}
	
	public void setC(double firstSecond){
		this.c = firstSecond;
	}
	
	public double getC() {
		return this.c;
	}
	
	public void setD(double secondSecond){
		this.d = secondSecond;
	}
	
	public double getD() {
		return this.d;
	}
	
	public void setE(double firstAnswer){
		this.e = firstAnswer;
	}
	
	public double getE() {
		return this.e;
	}
	
	public void setF(double secondAnswer){
		this.f = secondAnswer;
	}
	
	public double getF() {
		return this.f;
	}
	
	public boolean isSolvable() {
		if((a * d) - (b * c) == 0) {
			return false;
		}
		else
			return true;
	}
	
	public void setX(){
		
		if (isSolvable() == false){
			System.err.println("The equation has no solution");
		}
		
		else
			x = ( (e * d) - (b * f) ) /( (a * d) - (b * c) );
	}
	
	public double getX() {
		return this.x;
	}
	
	public void setY(){
		
		if(isSolvable() == false) {
			System.err.println("The equation has no solution");
		}
		else
			x = ( (a * f) - (e * c) ) / ((a * d) - (b * c));
	}
	
	public double getY(){
		return this.y;
	}
	
	public void tester() {
		
		LinearEquation x = new LinearEquation(10, 10, 10, 10, 100, 100);
		
		System.out.println(x.getX());
		System.out.println(x.getY());
	}
	
}
	

I think I found the solution to my other problem.

numberOfIncompletes = 0;
for(k = 0; k < incompletes.length; k++) {
if(studentID == incompletes[k]) {
numberOfIncompletes ++ ;
}
}

The code compiled fine. I keep thinking of arrays as something different I should just look at them as a collection of variables. BTW good catch with the error in spelling I would not have caught that.

numberOfIncompletes = 0;
if(studentID == incompletes[]) {
for (k = 0; k < incompletes.length; k++) {
numberOfIncompletes += incompletes[k];
}
}

Thank you for your input. I have another question regarding changing the values of an array. This is the question.
Given
*an int variable k ,
*an int array incompletes that has been declared and initialized,
*an int variable studentID that has been initialized, and
*an int variable numberOfIncompletes ,
write code that counts the number of times the value of studentID appears in incompletes and assigns this value to numberOfIncompletes .

You may use only k , incompletes , studentID , and numberOfIncompletes .
This is my code, but I know its off by a lot.

numberOfIncompletes = 0;
if(studentID == incompletes[]) {
for (k = 0; k < incompletes.length; k++) {
numberOfIncompletes += incompletes[k];
}
}