Question 1019767
Try to identify the job.  What is doing the job?  Maybe, say the flame is doing a job of consuming length of the candle.  


You want to think with RT=L to relate rate, time, length.


Rate is  {{{0.5(inches/hour)}}}.
Some data is  time {{{1/12}}} hours, {{{x-3.5}}} inches consumed.  Think how that makes sense, before continuing.


...


The situation as equation including the units of measure,
{{{0.5(inches/hour)*(1/12)*hour=(x-3.5)*inches}}}, using x for the length of the candle originally.


And then just the numbers without the units,
{{{0.5(1/12)=x-3.5}}}
which should be easy to solve.