Originally Posted by Nautigal
Yes, it simply depends on which is the basis for comparison. "How many more" is using the smaller as the basis for the comparison, therefore "small plus blank equals large".

"How many fewer" would be comparing based on the larger, therefore "large minus small equals blank" or "large minus blank equals small".

Yes, exactly, thank you! That is exactly (well, almost exactly, you say it a bit more clearly and succinctly), what the texts and teaching materials say.