Ответ:

  1. 306 + 98 = 404; 404 + 131 = 535; 535 + 409 = 944.
  2. 51 + 309 = 360; 360 + 48 = 408; 408 + 7 = 415.
  3. 630 + 205 = 835; 835 + 90 = 925; 925 + 75 = 1000.