[ Diff(x[1], t) = (-1)*k[7]*k[3]*x[1]*x[3]/x[6]/k[7],
  Diff(x[2], t) = (1*k[7]*k[3]*x[1]*x[3]/x[6] + (-1)*k[7]*k[4]*x[2])/k[7],
  Diff(x[3], t) = (1*k[7]*k[4]*x[2] + (-1)*k[7]*k[5]*x[3] + (-1)*k[7]*k[6]*x[3])/k[7],
  Diff(x[4], t) = 1*k[7]*k[5]*x[3]/k[7],
  Diff(x[5], t) = 1*k[7]*k[6]*x[3]/k[7],
  Diff(x[6], t) = 0/k[7] ]