Question

Where in the sentence should the writer add a hyphen?

Answer 1

"...he spends two-thirds of his time....” because hyphens are added when writing out fractions.

Answer 2

The correct answer is: two-thirds

Hyphens are used to link words and parts of words, they show the reader that two or more elements in a sentence are related. Following the grammatical rules, they can be used when a fraction is spelled, except when a or an is used to introduce it.

For example:

I gave you one-third of my cake.

I gace you a third of my cake.

In a or an is not used so a hyphen can be used.