{ diff(x1, t) = (-1)*100*exp((-t)/90)/k5,
  diff(x2, t) = ((-1)*k7*x1*x2/(k8 + x2) + 1*(k9*x7 - k10*x2))/k5,
  diff(x3, t) = (1*k7*x1*x2/(k8 + x2) + (-1)*(k13*x3*x4 - k14*x5))/k5,
  diff(x4, t) = (1*(k11*x9 - k12*x4) + (-1)*(k13*x3*x4 - k14*x5))/k5,
  diff(x5, t) = (1*(k13*x3*x4 - k14*x5) + (-1)*k15*x5)/k5,
  diff(x6, t) = (1*k15*x5 + (-1)*(k16*x6 - k17*x9*x8))/k6,
  diff(x7, t) = ((-1)*(k9*x7 - k10*x2) + 1*k18*x8/(k19 + x8))/k6,
  diff(x8, t) = (1*(k16*x6 - k17*x9*x8) + (-1)*k18*x8/(k19 + x8))/k6,
  diff(x9, t) = ((-1)*(k11*x9 - k12*x4) + 1*(k16*x6 - k17*x9*x8))/k6,
  diff(x10, t) = 1*k18*x8/(k19 + x8)/k6 }