To find the total number of people who prefer the seaside or an island, we will add the number of people who prefer those destinations for both activities (hiking and swimming).
Seaside:
- Hiking: 20
- Swimming: 53
Total for Seaside = 20 (Hiking) + 53 (Swimming) = 73
Island:
- Hiking: 12
- Swimming: 40
Total for Island = 12 (Hiking) + 40 (Swimming) = 52
Now we add the totals for both seaside and island:
Total for Seaside or Island = 73 (Seaside) + 52 (Island) = 125
Therefore, 125 people prefer the seaside or an island.