Answer:
it will take 70 years for people on Earth to see the spaceship reach its destination.
Explanation:
Time = Distance / Speed
In this case, the distance is 30 light years and the speed is 0.75 light years per year:
Time = 30 light years / 0.75 light years per year
By performing the division, we find that it will take the spaceship 40 years to reach the star from Earth.
However, it's important to note that the people on Earth will not see the spaceship reach its destination until light from the spaceship's arrival travels back to Earth. Since the star is located 30 light years away, it will take an additional 30 years for the light from the spaceship's arrival to reach Earth.
Therefore, the total time it will take for people on Earth to see the spaceship reach its destination will be the time it takes the spaceship to travel (40 years) plus the time it takes for the light to reach Earth (30 years).