"Are" is correct for most compound subjects, except for singular meanings (i.e. mac and cheese is) and alternative subjects (you or your wife is -- you or your friends are, though -- matches subject closest to the verb).
Yay for style manuals.
"Remain a cool kid" is preferred in American English. I've seen "Remain as" used in Commonwealth English, although I don't know whether it's considered more acceptable than "remain" alone.
We say the two fares are XXX, so the question should be asked with are as well.
The construction how much is the two fares may be seen as an ellipsis of how much is the total of the two fares and I would avoid this in formal writing.
Best Answer
"Are" is correct for most compound subjects, except for singular meanings (i.e. mac and cheese is) and alternative subjects (you or your wife is -- you or your friends are, though -- matches subject closest to the verb). Yay for style manuals.