Geometry

Question Analysis  
This question integrates complementary probability with multi - category outcomes.
The goal is to calculate the probability of avoiding a specific category ("blue") by considering all other categories ("green" and "red").  

Key Concept Explanation  
For events with multiple sub - categories, the complement of one category includes all other categories.
Here, "not blue" = "green or red," so we sum their counts.
For discrete events, this can also be calculated by counting outcomes that are not favorable to and dividing by the total number of outcomes.    

Step - by - Step Solution  
1. Total marbles: .  
2. Number of blue marbles: .  
  .  
3. Complementary probability (not blue):  
   
  Alternative method: Count green + red marbles:

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