53. Найдите неизвестное: 328 + x = 931; x + 295 = 1000; x − 267 = 399; x − 451 = 249; 613 − x = 317; 37 + x = 685.

1. 328 + x = 931

   x = 931 − 328 = 603.

2. x + 295 = 1000

   x = 1000 − 295 = 705.

3. x − 267 = 399

   x = 399 + 267 = 666.

4. x − 451 = 249

   x = 249 + 451 = 700.

5. 613 − x = 317

   x = 613 − 317 = 296.

6. 37 + x = 685

   x = 685 − 37 = 648.

Ответ: 603; 705; 666; 700; 296; 648.