1. Start with the hexanoic acid backbone:

- Draw a six-carbon chain (6 C's connected by single bonds).

- Add a carboxyl group (-COOH) to the first carbon.

2. Add the ethyl group:

- On the third carbon of the chain, add a two-carbon branch (CH3-CH2-).

3. Complete the structure:

- Add the necessary number of hydrogen atoms to each carbon to complete their valency (4 bonds for each carbon).

Here's the final line-bond structure:

```

CH3

|

CH3-CH2-CH-CH2-CH2-COOH

|

CH3

```

Explanation:

- Line-bond: Each line represents a single bond between two atoms.

- Carbon: Carbon atoms are implied at the intersections of lines and at the ends of lines.

- Hydrogen: Hydrogen atoms are not explicitly shown unless they are attached to a heteroatom (like oxygen).

- Other atoms: Oxygen and the carbon of the carboxyl group are explicitly drawn.

Let me know if you have any other molecule you'd like to draw!