Explanation:

- Background Information: The average age of two people five years ago was 7.5 years.

- Calculation Breakdown:

- Five years ago, their combined age was \(7.5 \times 2 = 15\) years.

- After five years (i.e., present day), their combined age becomes \(15 + (5 \times 2) = 25\) years.

- Five years into the future, their combined age will be \(25 + (5 \times 2) = 35\) years.

- Therefore, their average age after five years is \(35 / 2 = 17.5\) years.

- Options:

- Option 1: 18 years

- Option 2: 17.5 years

- Option 3: 18.5 years

- Option 4: 17 years

- The correct answer is Option 2: 17.5 years.