1. **State the problem:** We have a rectangular garden with a perimeter of 18 yards. The top side length is 6 yards, and the left side length is $x$ yards. We need to find the value of $x$. 2. **Formula for perimeter of a rectangle:** $$P = 2(\text{length} + \text{width})$$ where $P$ is the perimeter. 3. **Apply the formula:** Given $P = 18$ yards, length = 6 yards, width = $x$ yards, $$18 = 2(6 + x)$$ 4. **Simplify the equation:** $$18 = 12 + 2x$$ 5. **Isolate $x$:** $$18 - 12 = 2x$$ $$6 = 2x$$ 6. **Divide both sides by 2:** $$\cancel{2} \times 3 = \cancel{2} x$$ $$3 = x$$ 7. **Answer:** The length $x$ is 3 yards.