Final answer:
The recipe cost of scallions can be found by dividing the cost of a bunch by the number of scallions in the bunch and then multiplying it by the number of scallions required in the recipe.
Step-by-step explanation:
In order to find the recipe cost of scallions, we need to calculate the cost per scallion using the given information. We know that a bunch of scallions contains 12 scallions and the cost of each bunch is $0.90. So, the cost per scallion can be found by dividing the total cost of a bunch by the number of scallions in the bunch: 0.90 / 12 = $0.075 per scallion.
Next, we need to find the recipe cost of scallions which requires 4 scallions. To find the cost, we multiply the number of scallions required by the cost per scallion: 4 * 0.075 = $0.30.
Therefore, the recipe cost of scallions is $0.30.