What's the easiest way to learn how to play piano at an older age?

Starter books or a teacher

when ur at an older age, you can grasp the concepts easier, teachers are expensive, well the good ones are

just go with starter books and looking up videos on the web
but if your willing to pay for a teacher, go ahead, but only the good teachers will be strict with you

Actually its the other way around. You grasp concepts easier at a young age.

Correct, it all has to do with how your brain develops over time. Treat music like learning a foreign language, when you are young your brain is still malleable so learning things is actually easier and eventually those skills "hardwire" into your brain as an adult all those pathways are now set and do not change easily, so while it's very possible to learn new skills like learning an instrument the learning curve becomes harder...... now if you already know how to play another musical instrument at a fluent level then learning almost any number of instruments is already that much easier than someone starting from scratch since most of the groundwork is already set. I started playing guitar and bass guitar at the age of 7, and as an adult I have been able to teach myself very easily how to play the piano, drums, and violin without too much difficulty and at a competent level.