Q. There maths classes : X,Y,z take angebra test. The average score of class X is 83. The average score of class Y is 76 . The average score of class Z is 85. The average score of class X and Y is 79 and average score of class Y and Z is 81. what is average score of classes X,y,Z ?

1. 81.5
2. 80.5
3. 83
4. 78