import numpy as np
from scipy.special import erfinv

mu=100
sigma=(80-mu)/(np.sqrt(2)*erfinv(-0.8))
print('sigma = ',sigma)       

sigma =  15.60608292144758

xg=erfinv(2*0.9995-1)*sigma*np.sqrt(2)+mu
print('hranice geniality = ',xg)

hranice geniality =  151.35223302690287