Description: Sal evaluates 9.087 + 15.31 using the standard algorithm. Created by Sal Khan. Now, one thing I want to point out, some of you all might have seen these numbers all lined up and immediately want to say, hey, 7 plus 1 is 8, and 8 plus 3 is 11, carry the 1, et cetera, et cetera. Because, you see, right over here, these decimals aren't lined up. Here, if you did that, you would be adding the 7 thousandths to 1 hundredths.*Teacher Advisor is 100% free.