Explanation:

To find Satish's percentage gain, follow these steps:

- Initial Cost: Satish bought 35 notebooks for Rs700.

- Cost per Notebook: Rs700/35 = Rs20.

- Selling Price: He sold 28 notebooks for Rs600.

- Cost Price for 28 Notebooks: 28 * Rs20 = Rs560.

- Profit: Rs600 - Rs560 = Rs40.

- Percentage Gain Formula: (Profit/Cost Price) * 100 = (40/560) * 100 ˜ 7.14%.

Let's relate this to the options:

- Option 1: \(7\frac{1}{7}\)% (7.14%)

- Option 2: \(9\frac{1}{7}\)% (9.14%)

- Option 3: \(6\frac{1}{7}\)% (6.14%)

- Option 4: \(8\frac{1}{7}\)% (8.14%)

Correct Answer: Option 1: \(7\frac{1}{7}\).