You suggested I hadn't made it out of primary school yet, presumably because my math example was a trig/algebra example.

This came off as gloating over your own math skills.

I let you know it came off as immature by asking you if that was your way of telling us that you had failed more difficult math classes, like diff eqs.

I then closed by letting you know that not only am I beyond primary school, I found a notoriously difficult math curriculum (again, diff eqs) to be just as easy as the trig/calc that made me fall for math in then first place.

Finally, I suggested that all math is easy if you're good at math, and that if you found something in math challenging, it'd be because you personally struggled with it and not because it didn't make perfect sense, to tie the whole point together.

Hope this helps.