C#: method name should be PascalCase (Please refer to implementation of backward compatibility here )

Actual and expected are swapped

Please use appropriate datatypes and encodings.

You want two numbers. They should be returned as a pair ( a tuple in some languages, a 2 element array in some flawed language(s) ); there is absolutely no reason to stringify them, especially in a kata aimed at beginners.

You might even want to ask for one number only, because the two numbers are not independent; by definition, the higher one is the lower one plus the input.

Teach good habits!

( Yes, it's worth it to invalidate all current solutions. That's what Beta is for. )

JS Example tests still use the legacy test framework.

Also, remove the comments. Anything useless in Example tests is just a distraction.