{ diff(x1, t) = (1*k2*(k3*k12*x2 - x1*x3)/(1 + k12 + x2 + x1 + x3 + k12*x2 + x1*x3) + (-1)*k6*(k7*x1 - k13)/(1 + x1 + k13) + (-1)*k8*(k9*x1 - k14)/(1 + x1 + k14))/k1,
  diff(x2, t) = ((-1)*k2*(k3*k12*x2 - x1*x3)/(1 + k12 + x2 + x1 + x3 + k12*x2 + x1*x3) + 1*k4*(k5*k15*x3 - k16*x2)/(1 + x3 + x2 + k15 + k16 + x3*k15 + x2*k16))/k1,
  diff(x3, t) = (1*k2*(k3*k12*x2 - x1*x3)/(1 + k12 + x2 + x1 + x3 + k12*x2 + x1*x3) + (-1)*k4*(k5*k15*x3 - k16*x2)/(1 + x3 + x2 + k15 + k16 + x3*k15 + x2*k16) + (-1)*k10*k11*x3)/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 }