epo=1/(1+(B/h)^n)

barB=3 10^9 120

dB=s0+s1 epo-d B==0

H=Solve[dB/.{B->barB,d->1/120,s0->10^9,s1->9 10^9,n->5},h]

N[H]

H11=barB(d barB-s0)/(s0+s1-d barB)/.{B->barB,d->1/120.,s0->10^9,s1->9 10^9}