Awriter should hyphenate a compound modifier that

contains an adverb ending in -ly.
comes after the noun it modifies.
comes before the noun it modifies.
contains an adjective ending in -ive.

A writer should hyphenate a compound modifier that comes before the noun it modifies.

For example:

Can I get a twenty-dollar bill?

As you can see in this example, the compound modifier twenty dollar modifies the noun bill which is located after it, which is the reason why it has to be hyphenated.

a compare and contrast essay is a piece of formal writing in which the author focus on the similarities between two ideas, objects, places, etc., and the differences between them. there are some aspects that the author should take into account when he/she is crafting the essay. first, the author has a clear idea of the effect that he/she wants to produce on the audience (a purpose). his/her main idea should be presented in the thesis statement in a simple but effective way which gives the audience a clear idea of the content and the direction of the essay. in addition, it is also important to focus to the similarities and differences that not only are interesting and relevant to the reader but also provide a new, impressive point of view or deeper understanding of a topic.