{ diff(x22, t) = 0/k30,
  diff(x1, t) = 1/(1 + k13)*(k8/(171/1000)*(k13*x20^2 + x15^2) - k8*(k13*x13 + x11)),
  diff(x2, t) = 1/(k13 + 1)*(k8/(171/1000)*(k13*x18*x20 + x15*x21) - k8*(k13*x17 + x16)),
  diff(x3, t) = 1/(1 + k13)*(k13*k6*x26*k17/(k17 + x22)*x6 - k7*x15),
  diff(x4, t) = k1*(k27 + k26*x16 - (k18*x9 + k25)*x4),
  diff(x5, t) = k1*((1 - k5)*(1 - k16) - (k4 + 1 - k28)*x5),
  diff(x6, t) = k2*x10 - (k3 + k6*x26*k17/(k17 + x22))*x6,
  diff(x7, t) = k1*(k4*x5 - (1 - k28)*x25 - k18*x4*x9),
  diff(x8, t) = k6*x26*k17/(k17 + x22)*x6 + k2*x15 - k3*(x20 + k11*(x17 + 2*x13)),
  diff(x13, t) = k8/(171/1000)*x20^2 - (k8 + k3*k11)*x13,
  diff(x17, t) = k8/(171/1000)*x18*x20 - (k8 + k3*k11)*x17,
  diff(x19, t) = k3*x21 - k3*(x18 + k11*x17),
  diff(x24, t) = k1*(k18*x4*x9 - (k22 + k12*(1 - k28))*x24),
  diff(x26, t) = k1*(k22*x24 - k12*(1 - k28)*x26) }