Answer:
6 strawberries
You subtract 32 from 56, which gives you 24. Then, if one strawberry is 4 calories, you can eat 6 of them to gain 24 calories.
32 + 24 = 56 ... So one plum (32) and six strawberries (4+4+4+4+4+4) gives you 56 calories, which is the total. That's how you can check your work.
Answer: 6