20 because if your rounding to the nearest 10 the range you have is 10-20 because 17 is in between 10 and 20, then you can count or just tell which one 17 is closer to: 17-10=7 so 17 is 7 away from ten, then 20-17=3 so 17 is three away from 20. so now you choose the answer that is closer to the number:)
