I agree; the whole thing could be done with pictures rather than numbers. Lay out an actual grid, with objects -- seven ladybugs in the third row, fourth colum

I agree; the whole thing could be done with pictures rather than numbers. Lay out an actual grid, with objects -- seven ladybugs in the third row, fourth column, etc. When you subtract one row from another, you physically drag the ladybugs from one row over the other row, and when they 'match' they disappear. You can tap into physical intuition.