First of all, read the statement and understand what it means.
"The temperature was at least 36 degrees" means the temperature was 36 degrees or more, that is, "greater than or equal to 36 degrees".
Second. understand that we are comparing "temperature" to "36 degrees". That is, the variable will represent temperature. I like to use single-letter variable names that remind me of what they represent, so I would choose "t" or "T". You can use "kay" to remind you of something hot, or "splat" or "q" or anything else you might choose. It doesn't have to be a single letter, nor does it have to make any sense. (Later, when you revisit the problem, it works better if it *does* make sense.)
We've already figured out we want the comparison to be "greater than or equal to", so we need both the > symbol and the = symbol.
Of course, the number is 36, since you are told to use the number given. In some problems, you may want to convert the number to different units before you put it in the comparison.
T ≥ 36
