not ... at all

even if ...,...cannot

difficult / hard, probably impossible

very, exceedingly, awfully / (before a negative form) not at all, at all, by no means

question, problem on homework etc. / a question; a matter (of time etc.) / a problem (something that needs to be dealt with); a trouble / an issue; a matter

unthinkable, out of the question

(informal) no problem

practical question (problem)

matter of life or death / (idiomatic) an extremely urgent matter

viewing as a problem