Answer:
30 clovers
Explanation:
If Nathaniel find 2 four-leaf clovers in the first 12 minutes of his search, the rate at which he finds the four-leaf clovers is:

To predict the number of four-leaf clovers Nathaniel will find in 180 minutes, multiply the found rate by 180 minutes:

Therefore, Nathaniel will find 30 clovers in 180 minutes based on the rate at which he found 2 clovers.