Final answer:
To find how much Mrs. Johnson should use, we need to find half of 3/4 cup. Mrs. Johnson should use 3/8 cup of peanut butter.
Step-by-step explanation:
To find how much peanut butter Mrs. Johnson should use, we need to find half of 3/4 cup. To do this, we can multiply 3/4 by 1/2. Multiplying the numerators (3 * 1) gives us 3, and multiplying the denominators (4 * 2) gives us 8. So, Mrs. Johnson should use 3/8 cup of peanut butter. Therefore, the answer is (C) 3/8 cup.