Answer:
let's say you have 3 flavors
- chocolate
- vanilla
- strawberry
lets say you have 5 toppings
- nuts
- carmel
- chocolate chips
- strawberries
- sprinkles
now you have the choice of having whip cream or no whip cream.
so what you do is start with the flavor vholctae go to the topping nuts then whip cream. now do the same thing but with no whip cream.
do the same with each flavor and at the end you have 20 combinations.