You do not hyphenate the number.
responsible
According to the sources I've found on a quick search, you should hyphenate 'coauthor', i.e., it would better be: "co-author".
eleven
As a mother of 3 kids i think its appropriate to talk to them about that at thae age of about 10 or 11...but that's up to you
You do not need to hyphenate.
You do not hyphenate the number.
You hyphenate it only at the hyphen.
Don't hyphenate; ongoing is one word.
I think it's more accepted to hyphenate it.
Can you, or should you? You can hyphenate it if you're moving between lines in a paragraph and need to break up the word. You shouldn't hyphenate it normally.
You would hyphenate "thank you" when it is used as an adjective before a noun, such as in "a thank-you card."
You mean at the end of a line? Well it depends on how much room you have hyphenate at a syllable is probably best. If you have little space before the end of the line don't hyphenate a word. You could hyphenate like this trans- portation.
No...
The appropriate age for a girl to get her ears pierced is 8.
In my opinion, an appropriate age would be 12 or 13.
You can hyphenate 3 bedroom when it is used in a list. It is usually not hyphenated when it is used by itself.