See below.
Here is the program with the
part for reading x filled in:
import java.io.*;
class EvalPoly
{
  public static void main (String[] args )  
  {
    Scanner scan = new Scanner ( System.in );
    double x;                      // a value to use with the polynomial
    double result;                 // result of evaluating the polynomial at x
    String response = "y";         // "y" or "n"
    while ( response.equals( "y" ) )    
    {
       // Get a value for x.
       System.out.println("Enter a value for x:") ;
       x = scan.nextDouble();
       // Evaluate the polynomial.
       result = ;   
       ;
       // Ask the user if the program should continue.
       System.out.println("continue (y or n)?");
       response = scan.nextLine();      
    }
  }
}
Remember what the problem is: You are interested in the value of the polynomial
7x3- 3x2 + 4x - 12
for various values of x. Only two blanks remain to complete the program.
Complete the program by filling in the blanks.