It seem that no one here understands basic arithmetic, so I'll explain;
8 + 5 = 8 + (2+3) = (8+2) + 3 = 10 + 3 = 13
Now, you might be saying "Why go through all the trouble? I know that 8 + 5 is 13"
In which case I commend you on your masterful ability to do single-digit math.
So, now try "187 + 25"
Some of you are saying, "Well, 7 + 5 is 12, carry the one....um.. where's some paper...??.
"
And those who know how to do math in their heads are saying.
"That 187 + 13 + 12 which is 200 + 12 which is 212"
That's what Common Core is trying to teach.
I find it funny that most Americans hate math, and insist that they are no good at it, yet get incensed at it being taught any way other than the way the clearly failed for them.