Answer: 15 ways.
Step-by-step explanation:
Total number of hats owned =6
The number of hats taking on vacation=2
To find the different ways to choose 2 hats from 6, we use combination with n=6 and r=2, we get
The number of ways to choose 2 hats from 6=

Hence, in 15 ways we can choose 2 hats from 6 hats.
Hats 1,2,3,4,5,6
1,2
1,3
1,4
1,5
1,6
2.3
2,4
2,5
2,6
3,4
3,5
3,6
4,5
4,6
5,6
15 different combinations