Can an adult learn calculus?
If you can learn algebra II and trig, then you can learn calculus. Calculus, conceptually, isn't more difficult than algebra II (and it's a little easier than trigonometry); it just assumes that you really know algebra.
Can I learn calculus at 35?
Absolutely. I'll start by saying that I've met and taught people who were in there 30s (and above!) learning calculus for the first time. In most cases, there was no significant differences in the difficulties faces between older and younger students.
Can I learn calculus at 60?
Yes, you can learn. It just requires your full attention towards learning it. Nothing is impossible in this world so why you are confused about it that you can learn it or not. Be confident and start learning calculus, you just need to have a guide or a tutor who can help you to understand it well and in an easy way.
Is learning calculus at 14 good?
Taking basic derivatives and other computations with calculus are not very difficult. Calculus is a big subject and there's a lot to cover, some things are much more subtle than others. The rigorous theory behind calculus is called "analysis"; if you were successfully learning that at fifteen, I'd be very impressed.