If you visualise the CL curve then CLmax (or Vs) will be at critical alpha or the very peak of the graph. 1.3Vs is faster than Vs so it must be at a smaller CL. To determine the percentage you need to rearrange the lift formula.

L = CL x Vsquared (all other factors remaining constant)

So CL = L/Vsquared

We dont know the lift but at Vs we can assume unity so CL = 1/(1.3)squared and then x100 to get a percentage =59%