Addition and Subtraction are closely linked.
From any subtraction fact, we can normally get another subtraction fact and also two addition facts.
Look at the subtraction fact:
8 - 3 = 5
From this, we can also say that:
8 - 5 = 3
And we can also write these two addition facts:
3 + 5 = 8
5 + 3 = 8
This will work for any numbers, even much larger ones.
Example
Use the subtraction fact:
63 - 27 = 36
to work out the values of A, B, C and D.
63 - 36 = A
36 + B = 63
27 + C = D
Answer
From the subtraction fact:
63 - 27 = 36
We get the other subtraction fact:
63 - 36 = 27
and the two addition facts:
36 + 27 = 63
27 + 36 = 63
So
A = 27
B = 27
C = 36
D = 63
Does that make sense?