A guy I saw on YouTube says math is a trainable skill and not a genetic birth right and you can improve your math skills with training, thoughts?

In high school I believed my intelligence was set in stone and nothing I did would be able to raise it or lower it, but now I believe I can do things to raise my intelligence and I can do things to lower my intelligence. I also believe I can do things to boost my fitness level and I can do things to diminish my fitness level, while in high school, I believed my fitness capability was assigned at birth and nothing I did would make it better or worse.

A guy I saw on YouTube says math is a trainable skill and not a genetic birth right and you can improve your math skills with training, thoughts?
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