Explanation:

- Mean proportional: It finds a number 'x' such that \( a/x = x/b \). For numbers 10.8 and 4.8:

$$ x = \sqrt{10.8 \times 4.8} \approx 7.2 $$

- Third proportional: It finds a number 'y' such that \( a/b = b/y \). For numbers 2 and 4:

$$ y = 4^2/2 = 8 $$

- Sum: Add the mean and third proportional:

$$ 7.2 + 8 = 15.2 $$

- Options:

- Option 1: 10.2

- Option 2: 11.2

- Option 3: 8.2

- Option 4: 15.2