Question

Using 8-bit 2’s complement math, Subtract 17 from 8 (8-17)

Answer 1

8 in binary is 00001000
17 in binary is 00010001

Ones complement = Inverting all the bits in binary
                = 11101110

Twos complement = Ones complement + 1
                = 11101110 + 1
                = 11101111

So, -17 in binary is 11101111
We can write 8-17 as 8 + (-17)

00001000
11101111
----------
11110111
----------

So, the answer is 11110111 in binary.

Subtract 1 and invert the bits to get the decimal value of this negative binary.
11110111 - 1 = 11110110
Inverting 11110110:
The result is 00001001
So, The binary value of 00001001 is 9.

So, the answer in decimal is -9