Ayogurt shop offers 3 different flavors of frozen yogurt and 12 different toppings. how many choices are possible for a single serving of frozen yogurt with one topping?

Well, to put it simply , the combinations will be like this :

  Flavor 1                                   Flavor 2                               Flavor 3
                     +                +      
 12 Possibilities                         12 possibilities                  12 possibilities
 

So total choices Possible would be 12 x 3 = 36 choices 

hope this helps