He is viewing that situation as a serious problem.

He views that situation as a problem.

No problem, I will do that job.

That proposal is completely unthinkable.

As a practical question, how are we going to fund this project?

She used a bobby pin to tie her hair.

She bought a new hairpin.

I will pin this message.

She used a hairpin to tie her hair.

The food at this restaurant is a mixed bag, ranging from the best to the worst.