The goal is to raise AT LEAST $180, so this automatically indicates that the amount of keychains sold with the price must be the same or more than $180.
k = number of keychains
each keychain is $2.25
2.25k ≥ 180
divide both sides by 2.25 to get the k alone
k ≥ 80
The answer is 2.25k ≥ 180, k ≥ 80
(Hope this isn't confusing)