{ diff(x1, t) = ((-1)*k15*x1*(1 - k6*(k14*k9 + k14*(1 - (k9 + k10)) + k14*k10)/k5)*k3 + (-1)*k15*x1*(1 - (1 - k6*(k14*k9 + k14*(1 - (k9 + k10)) + k14*k10)/k5)*k3))/k19,
  diff(x2, t) = (1*k15*x1*(1 - k6*(k14*k9 + k14*(1 - (k9 + k10)) + k14*k10)/k5)*k3 + (-1)*k14*k9*x2 + (-1)*k14*k10*x2 + (-1)*k14*(1 - (k9 + k10))*x2)/k20,
  diff(x3, t) = (1*k14*k10*x2 + (-1)*k16*x3)/k21 }