[ Diff(x[1], t) = 1*k[15]*1/4*(1 - x[3] - x[1])/k[15],
  Diff(x[2], t) = 1*k[15]*(6*x[1]/(1 + 2*x[1])*(1 - x[2])/(k[14] + 1 - x[2]) - 3/2*x[2]/(k[14] + x[2]))/k[15],
  Diff(x[3], t) = 1*k[15]*(x[2]*(1 - x[3])/(k[14] + 1 - x[3]) - 7/10*x[3]/(k[14] + x[3]))/k[15] ]