Well, you already know how much she stuff per hour, but you still need to find out how much per minute. And in one hour, there are 60 minutes.
So you divide the amount in an hour by 60 minutes, meaning you divide : 228 ÷ 60 = ?
And once divided, you get 3.8. So that would mean that she stuffs 3.8 envelopes per one minute, so that means nearly 4, but since you aren't asked to round, I'd say to just go for the average rate, which is 3.8
