Ответ:

  1. $$5 \times 2 = 10$$
  2. $$10 : 5 = 2$$
  3. $$7 \times 3 = 21$$
  4. $$21 : 3 = 7$$
  5. $$3 \times 9 = 27$$
  6. $$27 : 9 = 3$$