Final answer:
To find two mixed numbers with different denominators that have a sum and difference of 3 4/5, we can test the options using common denominators. Option a, 2 3/4 and 1 1/5, is the correct answer.
Step-by-step explanation:
To determine two mixed numbers with different denominators that have a sum and difference of 3 4/5, we can start by finding two fractions that add up to 4/5 and subtract to 4/5. Since the denominators need to be different, we can't use option d. By testing the options using common denominators, we find that option a, 2 3/4 and 1 1/5, satisfies the conditions.