[ Eq(1*k12*x1 + 1*k12*x6 + 1*k12*x8 + 1*k12*x9 + 1*k12*x10, k12*k13),
  Eq(1*k12*x3 + 1*k12*x4 + 1*k12*x9, k12*k14),
  Eq(1*k12*x6 + 1*k12*x7 + 1*k12*x8 + 1*k12*x9 + 1*k12*x10, k12*k15) ]