Ответ:

  1. \(\square\cdot6=54\), \(\square=54:6=9\);
  2. \(\square:7=8\), \(\square=8\cdot7=56\);
  3. \(72:\square=9\), \(\square=72:9=8\);
  4. \(12\cdot\square=0\), \(\square=0\);
  5. \(10\cdot\square=80\), \(\square=80:10=8\);
  6. \(15:\square=15\), \(\square=1\).

Ответ: а) 9; б) 56; в) 8; г) 0; д) 8; е) 1.