Explanation:

Let's break down the equation step by step:

- Calculate \( \sqrt{14400} \):

- \( \sqrt{14400} = 120 \)

- Calculate \( \sqrt{8100} \):

- \( \sqrt{8100} = 90 \)

- Multiply \( 120 \times 90 \):

- \( 120 \times 90 = 10800 \)

- Calculate \( (60)^2 \):

- \( (60)^2 = 3600 \)

- Subtract \( 3600 \) from \( 10800 \):

- \( 10800 - 3600 = 7200 \)

- Calculate \( (80)^2 \):

- \( (80)^2 = 6400 \)

- Finally, solve for \( ? \):

- \( 7200 = ? + 6400 \)

- \( ? = 7200 - 6400 = 800 \)

- Therefore, the correct answer is:

- Option 4: 800