Answer 1

Move class `Exams` definition up before the line where Exams.average() was invoked. I'm just guessing class definition must preceed its usage.

Answer 2

Sony,

Move your function call

console.log(Exams.average(exam1, exam2, exam3));

To beneath the class definition and it runs fine 👍.

You can’t use hoisting with an unitialized class, this is because the class could be extended. Hopefully that makes sense.