Question 10

Given the octal equation:

Perform subtraction column by column from right to left (base 8):

1. Position 0 (units):

   $$6 - 4 = 2.$$

2. Position 1 (eights):
   $2 < 6$, so borrow $1$ from the next position (worth $8$ in base 8).

   $$(2 + 8) - 6 = 10 - 6 = 4.$$

3. Position 2 (sixty-fours):
   $5$ becomes $4$ after lending the borrow.

   $$4 - 3 = 1.$$

4. Position 3 (five-hundred-twelves):

   $$7 - 4 = 3.$$

Combining the digits gives:

This matches option C.