How do I use variables from class in another class?

Question

Example:

class Class1{

public:
int x = 7;
};

class Class2{
public:

int addition(int y = 5){

int sum = y + x;
return sum;
}
};
//When I try to run something like this it tells me that x was not declared in this scope.

Answer 1

In Class2, add:

Class1 class1instance;

and then call class property under the instance:

int sum = y + class1instance.x;