GPT-5 fails a very simple math question

ChatGPT Use cases and examples
1

This is more about capabilities rather a bug, so if you ask :

“5.10 + x = 5.9

find x”

GPT-5 answers -0.2 confidently…

3 Likes
2

I managed to get the product x = 0.79 by prompting this: use proof guided reasoning (PCA style). For the given equation, show: 1. Step by step symbolic manipulation

  1. Verification of arithmetic rules. 3. Substitution check to confirm equality. 4. Final boxed result. Equation: insert here. You can save this on custom auto math no need to type all this many times.