{ x11 = x5 + x10,
  x12 = x2 + x3 + x4 + x6 + x7 + x8 + x9,
  1*k17*x2 + 1*k17*x3 + 1*k17*x4 + 1*k17*x5 = k17*k19,
  1*k17*x6 + 1*k17*x7 + 1*k17*x8 + 1*k17*x9 + 1*k17*x10 = k17*k20 }