You can use the k mean and fold change number

Relative expression  refers to fold changes in mRNA expression between two conditions, for example unstimulated cells vs activated cells. To calculate fold change  from real-time PCR data, you first  subtract the CT value of the normalizer gene for each set of data, to get the delta CT value for each condition. Then, subtract the delta CT value of the unstimulated cells from the activated cells. This number is referred to as the delta delta CT value (ddCT). Fold change is 2-ddCT . Thus, if the ddCT  is -1, then the relative expression of the stimulated cells is 2 times the unstimulated cells.

Thank you by your answers. I'll do this mathematical ecuation.