They can be said to exist, at least as abstractions or ideas like
>>232 explained. We can then use these universal ideas for example when holding up five fingers to signify that we want to buy five apples for example. We can also attach symbols to these ideas to make them easier to use, so that the word five and the symbol 5, V, etc. can be used to refer to the idea.
Different philosophers have different views on the topic though:
http://existentialcomics.com/comic/36.