Probability of not picking up a red marble = 8/15
No of red marbles = 7
No of green marbles = 5
No of blue marbles = 3
Total sample space = 3+7+5 = 15 marbles
Probability of picking out blue marble = 3/15
Probability of picking out red marbles = 7/15
Probability of picking out green marbles = 5/15
Probability of not picking up a red marble = 1 - 7/15 = 8/15
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