Problem solving

"A problem is only a problem (as mathematicians use the word)
                                                        (as opposed to what google thinks)
if you don't know how to go about solving it.
A problem that has no 'surprises' in store, and can be solved comfortably
by routine or familiar procedures (no matter how difficult!) is an exercise."

                            Alan Schoenfeld, 1983, For the learning of mathematics 3 pp. 40-47.