Add and subtract the same amount to both numbers in addition or subtraction to give a zero effect. Objective is to make a nice number, that is easier to work with. Example

7 + 8 =

(7+3) + (8-3)=

10 + 5 = 15

or

In subtraction, make the subtraend a nice number, (multiple of 10), subtract from the minuend. Then add the compensating number.

23 - 18

23 -( 20) + 2 =

3+2=5

7 + 8 =

(7+3) + (8-3)=

10 + 5 = 15

or

In subtraction, make the subtraend a nice number, (multiple of 10), subtract from the minuend. Then add the compensating number.

23 - 18

23 -( 20) + 2 =

3+2=5