Answer:
52.1 years .
Step-by-step explanation:
The time interval from 2020 to 2060 = 40 years. This will be the time as measured by an observer on earth.
For the person who is travelling at v = 2.5 × 10⁸ m/s,
t =40 √(1 - [(2.5 × 10⁸)² / (3.0 × 10⁸)²] = 22.1 years
Actual age for his counterpart on earth would be 30 + 40 = 70 years,
But space travel makes the astronaut to age slowly (time dilation) . So he appears to be 30 + 22.1 = 52.1 years old.