Ответ:

  1. a · 9 = a + a + a + a + a + a + a + a + a.
  2. 7 · k = k + k + k + k + k + k + k.
  3. (a + b) · 6 = (a + b) + (a + b) + (a + b) + (a + b) + (a + b) + (a + b).
  4. (x + z + 6) · 3 = (x + z + 6) + (x + z + 6) + (x + z + 6).