[ Eq(Derivative(x1, t), (1*k12*k2/(1 + (k6*(1 + (x3/k7)**k9))**k8) + (-1)*k12*k3*x1)/k12),
  Eq(Derivative(x2, t), (1*k12*x1 + (-1)*k12*k4*x2)/k12),
  Eq(Derivative(x3, t), (1*k12*k1*x2 + (-1)*k12*k5*x3)/k12) ]