-45 is that number which when added to +45 gives zero. Assuming we are using eight bits to represent a number calculate the twos complement of 45. First replaces 1s with 0s and vice versa.

0	0	1	0	1	1	0	1

Copy the result above into the top row below and then add 1 to your result.

+	0	0	0	0	0	0	0	1

Copy the result above into the second row below and add to demonstrate that 45 + (-45) = 0.

	0	0	1	0	1	1	0	1
+
	0	0	0	0	0	0	0	0

Repeat the steps above to find 75 (0s -->1s)

And add 1.

+	0	0	0	0	0	0	0	1

Next, add 45 and 75.

+

Does the answer above make sense? How do you know?