Ms. Hill travels 2400 miles at a rate of 400 miles per day to visit her grandchildren. How many days will it take to complete the trip.

That would depend on how many miles away her grandchildren live.

had you said, Ms. Hill travels 2400 miles at a rate of 400 miles a day to visit her grandchildren who live, (either 6 days away via car ... or even ... who live 16, 432 miles away) I'd have a destination.

but then again ... I could be wrong.

For this question, you just divide 2400 by 400 and get how many days it'll take! which, is 6