Step-by-step explanation:
3*4*2=24
Even if he doesn't use them all, he has 24 choices.
These kind of problems are permutation type problem. Order is not critical. Imagine yourself preparing such a meal. You have choices to be made in Sandwiches, fruits and drinks. It does not matter which order you set up the lunch box. It only matters that you chose.
You can't leave one out, nor does the problem allow you to trade (say) 2 drinks for one fruit.
