Answer:
Here we have a math thinking case.
Usually when we add two numbers, we try to deconstruct the numbers in such a way that the sum is easier. One thing that we always try to do, is to make a 10.
For example, in;
4 + 9
We know that 9 = 6 + 3
Then we can write:
4 + (6 + 3)
And re do the sum as:
(4 + 6) + 3
10 + 3 = 13
Now, we want to apply the same principle, but this time we don't want to make a 10.
We also can, for example, make a 5, like in:
2 + 13
We know that 2 + 3 = 5
then:
2 + 13 = 2 + (10 + 3) = 2 + 3 + 10 = 5 + 10 = 15
Other similar example:
2 + 7
We know that we can rewrite 7 as 3 + 4
Then:
2 + (7) = 2 + (3 + 4) = 2 + 3 + 4 = 5 + 4 = 9
This is not exactly easier, but in some cases can be useful.
