This free math tutoring video explains the three ways of thinking about subtraction (taking away, finding the difference, and whole/parts) and explains which one is best and why. I also talk briefly about why counting strategies are not as effective as visualization of quantities. There will be more on this topic in a later video.
Once again, Cuisenaire Rods come to the rescue and make everything easy. They are a treasure. If you don’t yet have some, go buy them!!!