∴∠AOB=90 +60 = 150,
∫OM average score ∠AOB,
∴∠aom= 1 ^ 2∠AOB = 75
∴∠MOC=90 -75 = 15,
And ∫ON∠BOC,
∴∠NOC= 1 2 ∠BOC=30,
∴∠MON=∠MOC+∠NOC= 15 +30 =45,
So the answer is: 45;
(2)∫∠AOC = 80,∠BOC=60,
∴∠AOB=80 +60 = 140,
∫OM average score ∠AOB,
∴∠AOM= 1 2 ∠AOB=70,
∴∠MOC=80 -70 = 10,
And ∫ON∠BOC,
∴∠NOC=∠BOC=30,
∴∠MON=∠MOC+∠NOC= 10 +30 =40,
So the answer is: 43;
(3)∫∠AOC = 70,∠BOC=50,
∴∠AOB=70 +50 = 120,
∫OM average score ∠AOB,
∴∠aom= 1 ^ 2∠AOB = 60
∴∠MOC=70 -60 = 10,
And ∫ON∠BOC,
∴∠NOC= 1 2 ∠BOC=25,
∴∠MON=∠MOC+∠NOC= 10 +25 =35,
So the answer is: 35;
(4) Conclusion ∠MON= 1 2 ∠AOC,
So the answer is: ∠AOC ..