[ Eq(Derivative(x1, t), (1*k18*k16*k8 + (-1)*k18*k1*x1*x5 + (-1)*k18*k2*x1*x6 + (-1)*k18*k8*x1)/k18),
  Eq(Derivative(x2, t), (1*k18*k1*x1*x5 + (-1)*k18*k3*x2 + (-1)*k18*k4*x2*x7)/k18),
  Eq(Derivative(x3, t), (1*k18*k3*x2 + (-1)*k18*k9*x3 + (-1)*k18*k4*x3*x7)/k18),
  Eq(Derivative(x4, t), (1*k18*k2*x1*x6 + (-1)*k18*k10*x4)/k18),
  Eq(Derivative(x5, t), (1*k18*k7*x3 + (-1)*k18*k13*x5)/k18),
  Eq(Derivative(x6, t), (1*k18*k6*x3 + (-1)*k18*k11*x6)/k18),
  Eq(Derivative(x7, t), (1*k18*k17*k12 + 1*k18*k5*x3 + (-1)*k18*k12*x7)/k18) ]