What is the purpose of that 12-3 homework assignment that went viral?

I teach this strategy in my first grade class. Some of my kids are so good at it and can now apply it mentally. It's a great strategy to know!

I don’t like how the 2 and 1 are written under the 3. That notation is typically used for factors.

My issue here isn’t with the strategy, it’s with the overscaffolding. The way it’s laid out on the page makes it needlessly confusing.

The 70’s continue to call

Some children will count backwards, some children will think of adding up (3+10=13, subtract 1), etc. Subtraction by decomposition as you are showing is wonderful provided we do not confine their way of thinking. Some students will benefit from this method, but others may not.

112 - 24. I do 100 - 12 = 88 taking 12 away from each, so start with a easy number

Nice idea, horrible ui/ux

This would benefit students who struggle to subtract when the top digit is less than the one being subtracted where they would have to “borrow”. Decomposing the 3 into 2 and 1 removes the barrier of having to borrow.

This is something I finally figured out on my own. I don’t subtract 7’s very well but 4’s and 3’s are easy for me.

I refer to this strategy as down over ten. Then I connect it to the next one the same way and call it down over 100. It is so useful with all numbers!