1. **State the problem:** A person pays 6000 per year towards a debt for 4 years, then pays 15000 per year. We want to find the year when the debt is completely paid off. 2. **Define variables and equation:** Let the total debt be $D$. After 4 years paying 6000 per year, the amount paid is $4 \times 6000 = 24000$. 3. **Remaining debt after 4 years:** $$\text{Remaining debt} = D - 24000$$ 4. **Payment after 4 years:** He pays 15000 per year. Let $x$ be the number of years after the first 4 years to pay off the remaining debt. 5. **Equation for total payment:** $$24000 + 15000x = D$$ 6. **Solve for $x$:** $$15000x = D - 24000$$ $$x = \frac{D - 24000}{15000}$$ 7. **Total years to pay off debt:** $$\text{Total years} = 4 + x = 4 + \frac{D - 24000}{15000}$$ Since the total debt $D$ is not given, the answer is expressed in terms of $D$. **Final answer:** The debt is completely paid off in year $$4 + \frac{D - 24000}{15000}$$.