First of all in order not to confuse yourself, define your variables at the top instead of initializing and defining them in the middle of your program.
example:
double Fr, Ar, En, Mth, Phy, Chi, His, Geo, Civ, Phi, Sp, Sg, My;
This is not a syntax error, but it is a good habit to define most of the variables you are going to use right at the top instead of the middle of the program. In case you have a variable that you are using as a constant. In case you are going to change that constant in your program to fit some other situation, you wont have to scroll through lines of code to change the value, you just find it at the top and change it :)
Another wrong thing is here:
My = (Ar + Fr + Eng + Mth + Phy + Chi + His + Geo + Phi + Sp)/31.5;
Replace the Eng variable name with En, since this is the one you defined and initialized before, you have nothing defined as Eng in your program so for sure the compiler wont allow this. And then your code should be able to compile without any errors.
Here is your code corrected:
import java.util.Scanner;
public class Carnetcalculator {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
double Fr, Ar, En, Mth, Phy, Chi, His, Geo, Civ, Phi, Sp, Sg, My;
System.out.print("Inserez votre notre de Francais: ");
Fr = input.nextDouble();
System.out.print("Inserez votre note d'Arabe: ");
Ar = input.nextDouble();
System.out.print("Inserez votre note d'Englais: ");
En = input.nextDouble();
System.out.print("Inserez votre note de Mathematiques: ");
Mth = input.nextDouble();
System.out.print("Inserez votre note de Physique: ");
Phy = input.nextDouble();
System.out.print("Inserez votre note de Chimie: ");
Chi = input.nextDouble();
System.out.print("Inserez votre note d'Histoire: ");
His = input.nextDouble();
System.out.print("Inserez votre note de Geography: ");
Geo = input.nextDouble();
System.out.print("Inserez votre note de Civisme: ");
Civ = input.nextDouble();
System.out.print("Inserez votre note de Philosophie: ");
Phi = input.nextDouble();
System.out.print("Inserez Votre note de Sport: ");
Sp = input.nextDouble();
Sg = (Mth + Phy + Chi)/17.5;
My = (Ar + Fr + En + Mth + Phy + Chi + His + Geo + Phi + Sp)/31.5;
System.out.println("Votre moyenne scientific est " + Sg + "Et votre Moyenne General est: " + My +".");
}
}
Another note is that it would have been much more elegant if you stored the grades in an array with the type double and then provide a for loop to fill in the array with the grades instead of writing the line input.nextDouble(); over and over again. You can also create a parallel array with the one you have to have it as a helper for storing the type of the grade on the respective index so that everything stays clear.
for example:
double grades = new grades[11];
String material = {"Arabe","Englais","Mathematiques","Physique","Chimie","Histoire","Geography","Civisme","Philosophie","Sport"};
Then for the user to fill out the grades all you need to do is something like this:
for(byte i = 0; i < grades.length; i++)
{
System.out.print("Inserez votre notre de " + material[i]);
grades[i] = input.nextDouble();
}
Thus eliminating all those lines of repetitive code :)
If you have any more questions just ask, just keep practicing and make sure you learn all the basics before shifting to more advanced stuff, never leave unfinished/un-understood stuff behind. And always remember: "A journey of a thousand miles begins with a single step" . Good luck and happy coding :)