means
"the exponent to which we must raise 'b' to get 'a'"
That's why
It's 2 because 2 is the exponent to which we must raise 5 to get 25.
Your problem
says in words:
8 raised to the exponent to which 8 must be raised to get 19.
When you do whatever it is necessary to do in order to accomplish
a task, you accomplish the task, right?
So when you do to 8 what you must do to 8 to get 19, then you
get 19.
Answer: 19.
Try to think through those words. It's tricky wording, but it's
a case of this:
"When you do what you have to do in order to get X, then
you get X."
Edwin