How to invoke method from another class

Question

https://code.sololearn.com/cx67wVD2pwtG/?ref=app
https://code.sololearn.com/cj14pAQN9Lpn/?ref=app

Answer 1

Create an object of that class

Answer 2

And call the method

Answer 3

It's showing "class is not found"?

Answer 4

https://www.sololearn.com/Discuss/2042486/?ref=app