Question 1168684
(5, 24)
(18, 16.2)
slope is -7.8/13=-0.6
after 12 hours it is -0.6*7 shorter than at 5 hours or 4.2 cm shorter or 19.8 cm  answer

the equation of the line is y-24=-0.6(x-5)
or y=-0.6x+27
the candle was 27 cm at 0 hours,
-0.6*5 or -3 (24 cm) at 5 hours
-0.6*18=-10.8 (16.2 cm) at 18 hours.'

the answer is 19.8 cm.