Button Click to Send User to Start of Program

I have an equations program that I'm working on, which randomly selects one of 50 equations, then takes the user through a series of scenes in order to solve it. Once the user solves the equation, they're asked if they want another equation. If they answer no, the program closes. If they answer yes, the program is supposed to randomly select another equation, then take them through the scenes to solve that one.

The program works just as I want it to the first time through. However, if the user selects "yes" for another equation, the program displays the END of the first scene, showing them the previous problem that they've already solved.

How can I send the user to the beginning of the scene, so that a new equation is randomly selected?

Here’s the relevant code for Scene 1:

package Equations;

import java.util.Random;
import javafx.application.*;
import javafx.stage.*;
import javafx.scene.*;
import javafx.scene.layout.*;
import javafx.scene.text.Text;
import javafx.scene.control.*;
import javafx.event.*;
import javafx.geometry.Insets;
import javafx.geometry.Pos;

public class equationsapp extends Application
    implements EventHandler<ActionEvent> {

    public static void main(String[] args) {
        launch(args);
    }

@Override public void start(Stage primaryStage) {

stage = primaryStage;

Random eqrdmzr = new Random();
int randomNumber = eqrdmzr.nextInt(3) + 1;

if (randomNumber == 1) {
isolCounterCoeff = 2;
isolVrblb = new Label("+");
isolCounter1a = 7;
isolCounter2a = 17;
slvCoeff = 2;
slvEqVrblTerm = new Text("2n");
slvEqWhlNmbrInt = 10;
slvEqWhlNmbr = new Text("10");
}

if(randomNumber == 2) {
isolCounterCoeff = 2;
isolVrblb = new Label("+");
isolVrblb.setVisible(false);
isolCounter1a = -18;
isolCounter2a = 4;
slvCoeff = 2;
slvEqVrblTerm = new Text("2n");
slvEqWhlNmbrInt = 22;
slvEqWhlNmbr = new Text("22");
}

if(randomNumber == 3) {
isolCounterCoeff = 3;
isolVrblb = new Label("+");
isolVrblb.setVisible(false);
isolCounter1a = -5;
isolCounter2a = 19;
slvCoeff = 3;
slvEqVrblTerm = new Text("3n");
slvEqWhlNmbrInt = 24;
slvEqWhlNmbr = new Text("24");
}

//Build Scene 1 - Top BorderPane
Text isolText = new Text("Isolate the Variable Term");
isolText.setStyle("-fx-font-size: 16pt");

//Build Scene 1 - Center BorderPane
Label isolCoeff = new Label();
isolCoeff.setStyle("-fx-font-size: 24pt;");
isolCoeff.setText(Integer.toString(isolCounterCoeff));

Label isolVrbl = new Label("n");
isolVrbl.setStyle("-fx-font-size: 24pt;");

isolVrblb.setStyle("-fx-font-size: 24pt;");
isolVrblb.managedProperty().bind(isolVrblb.visibleProperty());

Label isolEqIntLeft = new Label();
isolEqIntLeft.setStyle("-fx-font-size: 24pt;");
isolEqIntLeft.setPadding(new Insets(0, 10, 0, 0));
isolEqIntLeft.setText(Integer.toString(isolCounter1a));
isolEqIntLeft.managedProperty().bind(isolEqIntLeft.visibleProperty());

Label isolEqualSign = new Label("=");
isolEqualSign.setStyle("-fx-font-size: 24pt;");

Label isolEqIntRight = new Label();
isolEqIntRight.setStyle("-fx-font-size: 24pt;");
isolEqIntRight.setPadding(new Insets(0, 0, 0, 10));
isolEqIntRight.setText(Integer.toString(isolCounter2a));

//Build Scene 1 - Bottom BorderPane
Label isolLbl1 = new Label();
isolLbl1.setStyle("-fx-font-size: 22pt;");

isolEqIntLeft.setText(Integer.toString(isolCounter1a));
isolLbl1.setText(Integer.toString(isolCounter1b));

//Add the scene to the stage, set the title and show the stage
primaryStage.setScene(scene1);
primaryStage.setTitle("Equations");
primaryStage.show();

Here’s the event handler that’s supposed to send them back to the start of Stage 1:

Button yesBtn = new Button("Yes");
yesBtn.setStyle("-fx-font-size: 12pt;");
yesBtn.setOnAction(new EventHandler<ActionEvent>() {
public void handle (ActionEvent event) {
if (event.getSource() == yesBtn) {
stage.setScene(scene1);
}
}
});