Answer:
5
Explanation:
It is given that Joe goes to a mexican restaurant and order nachos. He can have just cheese or add any of the following: chicken, onion, sour cream or olives.
The different possible variations of nachos are:
1. Cheese
2. Cheese and Chicken
3. Cheese and Onion
4. Cheese and Sour cream
5. Cheese and olives
Therefore, total 5 different variations of nachos are possible.