for example Octal 7426 subtract Octal 4755, and just write the equation 7426-4755, and then 6 minus 5= 1,2 less than 5 borrow 8,8 -5+2=5, and the same goes for 4 because we borrowed 8 before, So subtract 1 to be tantamount to 3, borrow 8,8 -7+3= 4,7 borrow 1 to 6,6 -4=2, and the result is 2451