Using proportions to relate the amount of cups needed, it is found that she should use:
a) 0.25 cups of cereal.
b) 0.75 cups of water.
A proportion is a fraction of a total amount.
In this problem, for 4 servings, 3 cups of water and 1 cup of cereal is needed. One serving is one-fourth of the amount, hence:
Item a:
1/4 x 1 = 0.25 cups of cereal.
Item b:
1/4 x 3 = 3/4 = 0.75 cups of water.
More can be learned about proportions at https://brainly.com/question/24372153