Like many other words, it depends . . . If the words are used together as an adjective, they are hyphenated. "Alice bought a 90-cent picture frame." If the words are just nouns, they are not hyphenated. "Alice's picture frame cost 90 cents".
It is not hyphenated.
No it's not hyphenated.
Motorcycle is not hyphenated
words are only hyphenated when they have a separate meaning when separated than they do when hyphenated
hydro-electric station
Yes it should be hyphenated.
No, "hardworking" is not hyphenated.
It can be. Some words can be seen both hyphenated and non-hyphenated.
cost accumulation is the collecting and gathering of all cost and become collected
No. Well above is not hyphenated.
Yes it should be hyphenated.