hi im doing a post lab sheet for chem class. and im having a little trouble.

we did an experiment where we put a mixture into a bath and checked to see how long a color would leave from the mixture.
i have

temperature 12.6 C -> 285.6 K
Time 816 sec

but im supposed to find 1/T(K) it will be the x when i do a graph, but how do i find it? a classmate told me the answer is 3.50 x 10^-5 but she didn't have time to tell me how she solved it, i want to know because this might be in our class test.

if im missing any information, please let me know. just simple steps would be really helpful!