[ x[10] = x[1] + x[3],
  x[11] = x[2] + x[4],
  x[12] = x[8] + x[3] + x[4],
  x[15] = x[13] + x[14],
  x[16] = x[7] + x[13] + x[14],
  x[17] = x[9] + x[13],
  x[18] = x[9] + x[6] + x[13] + x[14],
  1*k[27]*x[6] + 1*k[27]*x[9] + 1*k[27]*x[13] + 1*k[27]*x[14] = k[27]*k[28] ]