Answer:
Number of Dinner Menu in the Restaurant = 4 =[1 appetizer+ 1 salad+ 1 main dish + 1 dessert]
Number of Different Appetizer = 6
Number of Different Salad =2
Number of Different Main Dishes = 3
Number of Different Desserts =4
Number of Different Dinner Outcomes
=[Choosing 1 appetizer among 6 appetizer] × [Choosing 1 Salad item among 2 salad Items] ×[Choosing 1 main Dish among 3 main Dishes] × [Choosing 1 dessert among 4 desserts]
=Order is not Important,so we will use the concept of combinatorics

So, Number of Possible Dinner Outcomes = 144