First, you divide 30.2 by 25. I'm sure your teacher wouldn't mind if you used a calculator for something like that.
We get 1.208, which can be rounded to 1.2 or 1.21. I'll say 1.21 because I like the hundredths place. XD
Now we know that each of the 25 servings are about 1.21 ounces of peanut butter. If you want to check your work if you didn't use a calculator, you can say, well, 1.21x25 is 30.25, which is very, very close to 3.2, and since we rounded, we can be sure the answer is correct.
Hope I helped!