Answer:
64
Explanation:
You want to know the number of ways Bree can choose to visit any or all of the remaining 6 countries on a trip to (possibly) seven countries when the order is specified.
Choices
Bree's itinerary will be of the form ...
- country 1
- country 2 – or not
- country 3 – or not
- country 4 – or not
- ...
- country 7 – or not
At each point in Bree's trip, she can make a choice to visit the country, or not. That is, there are 2 possibilities of outcome for each of 6 choices.
The total number of possibilities is ...
1 × 2 × 2 × 2 × 2 × 2 × 2 = 64
Bree can organize her trip in any of 64 different ways.
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