Using the same table:
| 0-9 years | 10-19 years | 20+ years | Total | |
|---|---|---|---|---|
| Group A | 7 | 14 | 9 | 30 |
| Group B | 6 | 4 | 20 | 30 |
| Group C | 17 | 12 | 1 | 30 |
| Total | 30 | 30 | 30 | 90 |
If one participant is selected at random, what is the probability that the participant is from group B, given that the participant is at least 20 years of age? (Express your answer as a decimal or fraction, not as a percent.)
