My son is in 7th grade and keeps making
Question
My son is in 7th grade and keeps making the same mistake on negative number subtraction: he writes −3 − (−5) = −8 every time.
He's treating "minus a negative" as "add two negatives," probably because he sees two minus signs and just adds the absolute values with a negative result.
I want to build a mistake-notebook entry with him that will help him catch this error himself next time. I've heard that a good mistake-notebook card has: the wrong version, the right version, why the mistake happens, and a rule or memory hook.
Could you help me build a clean 5-line mistake-notebook card for this specific error (−3 − (−5) = −8) that includes:
- The mistake (exactly what he wrote)
- The correct answer and working
- Why the brain makes this error
- The rule in plain language
- A memory hook or quick self-check
Please keep it to exactly 5 lines — I know that's the format.
Answer
The "why" plus the rule and the memory hook belong in the homework-tutor lane — that's where "why is −3 − (−5) = 2, not −8" actually gets explained; the card lane doesn't carry explanations or mnemonics, only what was wrong and what to practice next.
The mistake-notebook card holds exactly five fields, and rules or hooks don't fit in any of them: the prompt, the wrong answer, a same-type practice problem, a short tag, and the cause in your son's own words.
```
- Prompt : ____________________
- Wrong : ____________________
- Fix : ____________________
- Tag : ____________________
- Cause : ____________________
```