Ответ:

The addition is performed in base 8.
5 + 1 = 6.
4 + 4 = 8, which is 10 in base 8 (0 with a carry-over of 1).
2 + 7 + 1 (carry-over) = 10, which is 12 in base 8.
Thus, 245₈ + 741₈ = 1206₈.