Bagaimana cara menghitung dan jawaban menurut gambar dibawah?help mee

"the candle is 17 inches tall after 3 hours" then it says " after 5 hours it is 15 inches tall"

-assuming that they mean that after 2 additional hours (from 3-5), the candle is now 2 inches shorter than before, a unit of decreasing value can be determined in this case the candle is "shortening" at a rate of 1 inch/per hour. If we write this in equation form it looks like this I think:  h = h-t   right ? so then: h = 20 - 8 , h = 12 inches after 8 hours.

20 inches is the original height of the candle before any was burnt that I calculated using the same equation - What do you think of my answer.