1. **Stating the problem:** We want to find the depreciation rate $x$ using the straight line depreciation formula given the value of equipment decreases from 15000 to 5000 in 4 years. 2. **Straight line depreciation formula:** $$A = P(1 - in)$$ where $A$ is the amount after depreciation, $P$ is the initial amount, $i$ is the depreciation rate per year, and $n$ is the number of years. 3. **Substitute known values:** $$5000 = 15000(1 - 4x)$$ 4. **Expand and simplify:** $$5000 = 15000 - 60000x$$ 5. **Isolate $x$:** Subtract 15000 from both sides: $$5000 - 15000 = -60000x$$ $$-10000 = -60000x$$ Divide both sides by $-60000$: $$x = \frac{-10000}{-60000} = \frac{1}{6} = 0.1667$$ 6. **Interpretation:** The depreciation rate $x$ is 0.1667 or 16.67% per year. 7. **Explanation of 60000:** The term $60000$ comes from multiplying the initial value $15000$ by the number of years $4$: $$15000 \times 4 = 60000$$ This is because the straight line depreciation subtracts $i \times n$ times the initial value. --- **Final answer:** The depreciation rate using the straight line method is **16.67%** per year.