At a nature center, visitors chose either a bird walk or a garden walk. The table shows whether each visitor used the water-refill station.
| Walk chosen | Used the water-refill station | Did not use the water-refill station | Total |
|---|---|---|---|
| Bird walk | 18 | 12 | 30 |
| Garden walk | 9 | 21 | 30 |
| Total | 27 | 33 | 60 |
A visitor is selected at random from the visitors who used the water-refill station. Which choice is equal to the probability that the selected visitor chose the bird walk?