That happened with me and my kids! I actually complained that the teachers didn’t have a grasp on math. Most teachers were good with English, grammar and punctuation, but horrible with math.
As best as I could I taught my kids and grands multiplication tables in their head. My youngest granddaughter that I had anything to do with her education, she told me that an answer was was close enough. I explained to her why that is not true in no uncertain terms. I hope she remembers 5hat, as she is not living close anymore.