17 is a prime number. This means the only factors are 1, and 17. This means that since only 17, and 1 multiply to 17, to get a volume of 17 you can only use 1, and 17 (1, 1, and 17)
500 = 200 + 20h is our equation. Subtract 200 from both sides 300 = 20h Divide by 20 300/20 = 15. It will take 15 hours to get 500 points. Hope this helps!