{ 1*k6*x2 + 1*k6*x3 + 1*k6*x6 = k6*k88,
  1*k6*x8 + 1*k6*x9 = k6*k89,
  1*k7*x11 + 1*k7*x12 + 1*k7*x13 = k7*k90,
  8*k7*x11 + 4*k7*x12 + 4*k7*x14 + 4*k7*x15 + 8*k7*x16 + 4*k7*x17 + 4*k7*x18 + 4*k7*x21 + 4*k7*x22 = k7*k91,
  1*k7*x19 + 1*k7*x20 = k7*k92 }