Different fonts in the same Style in a Plot

Question

I have a plot, not important what it is and I have a linelegend as below:

PlotLegends -> 
Placed[LineLegend[{Style["K=3", FontSize -> 23], 
Style["K=5", FontSize -> 23], Style["K=7", FontSize -> 23], 
Style["K=9", FontSize -> 23]},

Here all "K" s must be italic but not "=" and the following numbers. In the usual case all are roman. How can I deal with this problem?

Answer 1

Plot[{3 x, 5 x, 7 x, 9 x}, {x, -1, 1}, 
 PlotLegends ->  Placed[LineLegend[Row[{Style["K", 23, Italic], 
        Style["=" <> ToString@#, 23]}] & /@ {3, 5, 7,   9}], {After, Top}]]

Or, use

PlotLegends -> Placed[LineLegend[
   Style[ToString[Style[K, Italic], StandardForm] <> "=" <> ToString[#], 23] & /@
     {3, 5, 7, 9}], {After, Top}]