It might also be worth mentioning that this particular child's frustration level is likely increased by living with a younger brother (2 year age difference) who IS math-talented, is a very quick thinker, can produce a lot of written work in a short time, and can answer most questions while big brother is still thinking. Big brother's weakness is often highlighted--at least he may feel that it is--because of little brother's talent. Sometimes I wonder how much that affects him. The frustration with challenge existed before little brother was of school age, so a lot of it is just in his makeup somehow, but I'm sure it is exacerbated by having a gifted younger brother (FSIQ in the 130's but has his own issues with hyperactivity/impulsivity and borderline OCD habits) in the house who has a talent for quick and accurate thinking--especially with math. Perhaps we should work harder on teaching him to appreciate his own talents and just focus on being the best version of himself, instead of worrying about comparisons. Easier said than done, but I do think this may be part of his unwillingness to get out of his comfort zone and work.
