I have an improvement suggestion to do about the exercise set "Relate addition and subtraction".

In this set, we can see questions like the following one:

7 - 2 = __ , because __ + 2 = 7.

However, I think the students can miss the main point of the related video about this set: Relating addition and subtraction.

Because of this, you guys could merge questions like this one I mentioned above with some questions like that:

If 4 + 3 = __ , then 7 - 3 = __ and 7 - 4 = __.

In that way, the student can realize more accurately the main (and most important) relationship about addition and subtraction: if you add 2 numbers, and subtract any of them from the result, you will get the other number. (Just like Sal mention in the end of the related video but, in my opinion, a little bit fast).

I hope you guys understand my point here.

Best regards,
Leo Maykell.