Answer:
4 years
Explanation:
subtract 3000 from 24000 then 3000 from the sum of each answer till you get to 12,000
after year 1: $21,000
24,000 - 3,000 = 21,000
after year 2: $18,000
21,000 - 3,000 = 18,000
after year 3: $15,000
18,000 - 3,000 = 15,000
after year 4: $12,000
15,000 - 3,000 = 12,000