{ diff(x1, t) = (1*k2*(k3*k14*x2 - x1*x3)/(1 + k14 + x2 + x1 + x3 + k14*x2 + x1*x3) + (-1)*k6*(k7*x1 - k15)/(1 + x1 + k15) + (-1)*k8*(k9*x1 - k16)/(1 + x1 + k16))/k1,
  diff(x2, t) = ((-1)*k2*(k3*k14*x2 - x1*x3)/(1 + k14 + x2 + x1 + x3 + k14*x2 + x1*x3) + 1*k4*(k5*k17*x3 - k18*x2)/(1 + x3 + x2 + k17 + k18 + x3*k17 + x2*k18))/k1,
  diff(x3, t) = (1*k2*(k3*k14*x2 - x1*x3)/(1 + k14 + x2 + x1 + x3 + k14*x2 + x1*x3) + (-1)*k4*(k5*k17*x3 - k18*x2)/(1 + x3 + x2 + k17 + k18 + x3*k17 + x2*k18))/k1,
  diff(x4, t) = 0,
  diff(x5, t) = 0,
  diff(x6, t) = 0,
  diff(x7, t) = 0,
  diff(x8, t) = 0,
  diff(x9, t) = 0,
  diff(x10, t) = (1*k10*k11*k19 + (-1)*k12*k13)/k1,
  diff(x11, t) = 0 }