I could not see any question in this. But I assume that you may want to know either the rate of burning or the total initial height of candle or how long it would take to burn the entire candle.
Assume that at time t=0 length of candle is `x`
Given at t=2 minutes, length is 8 inches
at t= 3 minutes, length is 7.25 inches
So the rate of burning of the candle or the rate at which the length of candle is decreasing = decrease in length / time duration
= (8-7.25)inches/(3-2) minutes
= 0.75 inches/minute
to find the initial length of the candle, use this formula for the times t=0 and t=2 minutes
the rate of change is same (given)
so, 0.75= (x-8)/(2-0)
solving this x= 9.5 inches
suppose it takes t` seconds to fully burn the candle
implies at t=t` length of the candle is 0 inches
so t`= .75 * 9.5 = 7.125 minutes or 7.13 minutes.
I hope this would help you.