Let's represent the length of the candle remaining unburned, in inches, t hours after the candle was lit as L. The rate at which the candle burns is 0.75 inches per hour, and its initial length was 9 inches.
We can write the equation for L in terms of t as follows:
L = 9 - 0.75 * t
This equation states that the length of the candle remaining unburned, in inches, t hours after it was lit is equal to the initial length minus the rate at which the candle burns, in inches per hour, multiplied by the number of hours that have passed.
For example, if t = 2, this equation becomes:
L = 9 - 0.75 * 2
= 9 - 1.5
= 7.5
This means that 2 hours after the candle was lit, it has 7.5 inches remaining unburned.