[ Eq(Derivative(x1, t), (1*k20*k2*k3**k4/(k3**k4 + x3**k4) + (-1)*k20*k5*x1/(k6 + x1) + 1*k20*k7*k8*1/2*(x4 + x8)/(k9 + k8*1/2*(x4 + x8)) + 1*k20*k10)/k20),
  Eq(Derivative(x2, t), (1*k20*k11*x1 + (-1)*k20*k12*x2/(k13 + x2))/k20),
  Eq(Derivative(x3, t), (1*k20*k14*x2 + (-1)*k20*k15*x3/(k16 + x3))/k20),
  Eq(Derivative(x4, t), (1*k20*k17*x1 + (-1)*k20*k18*x4/(k19 + x4))/k20),
  Eq(Derivative(x5, t), (1*k20*k2*k3**k4/(k3**k4 + x7**k4) + (-1)*k20*k5*x5/(k6 + x5) + 1*k20*k7*k8*1/2*(x4 + x8)/(k9 + k8*1/2*(x4 + x8)) + 1*k20*k10)/k20),
  Eq(Derivative(x6, t), (1*k20*k11*x5 + (-1)*k20*k12*x6/(k13 + x6))/k20),
  Eq(Derivative(x7, t), (1*k20*k14*x6 + (-1)*k20*k15*x7/(k16 + x7))/k20),
  Eq(Derivative(x8, t), (1*k20*k17*x5 + (-1)*k20*k18*x8/(k19 + x8))/k20) ]