Explanation:

- Let's denote the original number as \( x \).

- The number is decreased by 30%:

$$

x - 0.3x = 0.7x

$$

- Then, it is increased by 30%:

$$

0.7x + 0.21x = 0.91x

$$

- This new number, \( 0.91x \), is 72 less than the original:

$$

x - 0.91x = 72

$$

$$

0.09x = 72

$$

- Solving for \( x \), we get:

$$

x = \frac{72}{0.09} = 800

$$

- Option 1: 720 - Decreases and increases won't match conditions.

- Option 2: 800 - Calculation supported by steps above.

Correct Answer

- Option 3: 960 - Would yield a larger difference.

- Option 4: 1080 - Much larger decrease and increase offset.