Answer:
1156
Step-by-step explanation:
When Deucalion threw one stone over his shoulder, 8 people appear. So, for every stone, we have 8 new people.
Therefore, if Deucalion threw 68 stones, the number of people that would appear is

Instead, when Phyrra threw a stone, 9 people appear. So, for every stone, we have 9 new people.
Therefore, if Phyrra threw 68 stones, the number of people that would appear is

And so, we can now calculate the total number of people that appear after each had thrown 68 stones:
