This error occurs when No variable declaration or variable is outside of the scope you are referencing it in.
In your problem, the following Tuition function missed out argResidency parameter :
public Tuition(String argName, String argStudentNumber, String argCreditHours){
size=argName;
name=argStudentNumber;
residency=argResidency;
credithours="IC";
}
So your solution code is the following :
public Tuition(String argName, String argStudentNumber, String argCreditHours, String argResidency){
size=argName;
name=argStudentNumber;
residency=argResidency;
credithours="IC";
}