The sample space of an experiment or random trial is the set of all possible outcomes or results of that experiment.
The customer has 3 choices to make, first the soup, which has 2 possible outcomes(Tortellini and Lentil), then a salad, which also has 2 possible outcomes(Caesar and Macaroni), and finally a sandwich, which has 3 possible outcomes(Roast Beef, Ham and Turkey).
Since those 3 choices are independent, the sample space is given by the product between the possible outcomes of each step of the choice.
There are 12 combinations that a customer can make.