Answer:
The age difference will be 11.35 years
Step-by-step explanation:
From the point of view of Earth, Speedo's ship travelled 19.5 ly at 0.930c, thus it took it 19.5/0.930 = 20.97 years to arrive.
From the point of view of Earth, Goslo's ship travelled 19.5 ly at 0.715c, thus it took it 19.5/0.715 = 27.27 years to arrive.
But from Speedo's point of view it took him a different time to get to Planet X. This is calculated by the inverse of the time dilation transform:


And for Goslo:

The age difference will be 19.06 - 7.708 = 11.35 years