2016-01-22T18:40:28+08:00
5-10= ?
what is bigger? so it's 10 right? copy the sign of 10
and subract now! 10-5=5 and the sign is negative so -5
In subraction just look at the sign again
like this
-5-5=?
change the sign so it will be additiin
-5+-5=?
none is higher and their signs are same so -10
2016-01-22T19:12:12+08:00
6 + 5 = 11
4 + 9 = 13
-2 + (-8) = -10

In adding integers with unlike signs, subtract their absolute values (not sure if it's the right term but .. yea) then the sign of the integer having the higher absolute value among them will be the sign of their sum.
-10 + 8 = -2

10 - 8 = 2
Because -10 has greater value, the sign of their sum is negative
-10 + 8 = -2

another examples...
2 + (-9)
9 - 2 = 7
2 + (-9) = -7

5 + (-5) = 0

Subtraction:
We have the 3 C's.
C - copy the first integer
C - change the operation to it's reciprocal, from subtraction to addition
C - change the sign of the second integer.

5 - 3 = 2
5 + (-3) = 2 (just the same anyway...)

6 - 9
6 + (-9) = -3

8 - (-9)
8 + 9 = 15

10 - (-2)
10 + 2 = 12