Can someone please help me?! I keep trying to solve it but I keep getting the wrong answer

Question

Ok so, I've been trying to solve this math problem for over 30 minutes. I had this math problem last week and I skipped it. I asked on here but no one answered. I thought that if I came back to it I'd have a better understanding but I'm still just as stuck. Here's the problem:

Suppose that the height (in centimeters) of a candle is a linear function of the amount of time (in hours) it has been burning. After 15 hours of burning, a candle has a height of 18.5 centimeters. After 32 hours of burning, its height is 10 centimeters. What is the height of the candle after 28 hours?

Answer 1

15 hours 18.5 cm

32 hours 10 cm

28 hours x cm where 18.5<x<10 and x closer to 10 than 18.5

h(t) = y = mx +b

18.5 = 15m + b

10 = 32m + b

2 equations, 2 variables, solve by substitution, elimination or matrix algebra

18.5(32) =15(32)m + 32b

10(15) =32(15)m + 15b

subtract

32b-15b = 18.5(32)- 10(15

17b = 592-150=442

b = 442/17 = 26

10=32m+26

32m =10-26 =-16

m =-16/32 = -1/2

h(t) = -t/2 +26

h(28) = -28/2+26 =-14+26 = 12 cm after 28 hours

h(0) = 26 cm initially at time t=0