First one is: 
public void adjustAge(int Age) {
            age = Age + 20;
            System.out.println("The age in adjustAge() is " + age);//In this case this prints 40 as age here also.
        }
Second one is: 
public void adjustAge(int age) {
            this.age = this.age + 20;
            System.out.println("The age in adjustAge() is " + age);//the problem here is that this print only gives
                                                                                                  // 20 as the age in this particular method.
        }