Careless errors are excusable. But being arrogant about your careless error is another matter!

@bijouxbroussard

It is often the case that poor reading skills are part of why a student struggles with math.

@TrunkZ With only a two-second clip it is hard to know just what was going on - but was it made as a "joke" anyway?

(The sum is so obviously incorrect it may as well be!).

@ArishMell It is a common mistake that school children make. As for this clip, who knows?

@DrWatson Really?

Oh - thank you for that!

I had to study it quite carefully to see that the girl has treated it as a row of three separate sums, and totally missed the need to carry-over. It then struck me she seems to be trying to solve the sum from left to right - no wonder she's in a pickle.

Since it is now some 70 years since my first sums I forget what sort of mistakes were common to my class-mates and I, but I don't recall ever encountering that one. More likely we just made counting mistakes (e.g. "8+5 = 14"), or were puzzled by "8+5 = 13 but where does the 1 go?".

I do remember we were taught to write "H T U" above a three-digit number process to help us keep all the digits in their columns, to understand what the number means, and to comprehend carrying and borrowing.

Indeed, it was going back to that labelling that helped me much later in life finally to understand logarithms - no longer as times-sums tools but in certain technical calculations at work. That reason was salient too, for by giving me a real-life vantage-point over indices and logarithms I found them easier to understand... some four or five decades late!

@JimboSaturn I don't mind genuine incomprehension or ignorance as no-one can possibly know everything, but I don't like bragging about ones own ignorance, or trying to demean or ridicule the subject as a sort of mask. When it comes to mathematics, or even just arithmetic, that seems a particular trait among some celebrities.