Alternative method for subtraction regrouping
In elementary school (Germany) I also learned another method (besides the one here: https://www.khanacademy.org/math/arithmetic/arith-review-add-subtract/arith-review-subtract-within-100/v/introduction-to-regrouping-borrowing): You can write a ten above the minuend digit and a one under the digit on the left of the subtrahend digit. Then you add the ten to the minuend and the 1 to the digit on the left of the subtrahend digit. It's the same as if you broke apart the tens, but you only have to know single digit subtraction without carrying and two-digit addition. Additionally you don't have the mess of constantly needing to cross out and rewrite digits.
Here's an example: (from https://www.kapiert.de/media/image/0BD32134/E7F61FE2/78421961/F5EA74DD.png)
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