Which of the following scenarios represents a combination? the number of ways 30 people can finish in the first 3 positions. the number of possible pizzas that can be made with 12 possible toppings. the number of ways 15 people can line up in a row. the number of ways letter can be pulled from the tiles in a scrabble board.

The scenarios that represents a combination is:

The number of possible pizzas that can be made with 12 possible toppings.

Combination--

Combination refers to the selection or ways of choosing 'n' items.

                             whereas

Permutation--

Permutation refers to the selection as well as arrangement of n items.

1)

The number of ways 30 people can finish in the first 3 positions.

In this situation we need to use permutation.

Since firstly we have to choose  three people out of 30 who attained the top three positions and then we have to arrange them according to there ranks.\

2)

The number of possible pizzas that can be made with 12 possible toppings.

This situation will involve combination.

Because the toppings may be any random way we have to just choose the different number of toppings we require for pizza.

3)

The number of ways 15 people can line up in a row.

In this scenario we need to use permutation.

Because we have to arrange 15 people in a line.

4)

The number of ways letter can be pulled from the tiles in a scrabble board.

In this situation we'll use permutation.

Since we are asked to choose the letters from the board also the order in which the letters are chosen will vary.