{ 1*k12*x1 + 1*k12*x6 + 1*k12*x8 + 1*k12*x9 + 1*k12*x10 = k12*k13,
  1*k12*x3 + 1*k12*x4 + 1*k12*x9 = k12*k14,
  1*k12*x6 + 1*k12*x7 + 1*k12*x8 + 1*k12*x9 + 1*k12*x10 = k12*k15 }