Description: Just like when add, be sure you align decimals before subtracting. Created by Sal Khan and Monterey Institute for Technology and Education. We need to calculate 9.005 minus 3.6, or we could view it as 9 and 5 thousandths minus 3 and 6 tenths. So we've lined up the decimals, and now we're ready to subtract. And when you look at it that way, you'd say, OK, 5 minus 0 is nothing, and you just write a 5 right there.*Teacher Advisor is 100% free.