Answer:
14/21
Step-by-step explanation:
Total marbles = 7+8+6 = 21
7 Red
8 Green
6 Blue
Probability of choosing Red = 7/21
Probability of choosing Green = 8/21
Probability of choosing Blue = 6/21
Probability of choosing Green or Blue = 8/21 + 6/21 = 14/21