One and five tenths years OR one and one half years.
Fifteen
It's written as.. fifteen
15 = fifteen
fifteen minus b
fifteen million
" fifteen minus 'bee' "
Fifteen degrees.
One hundred seventy years.
One hundred fifty years.
Twenty-one years old.
You already have in the question.
The answer would depend on what period of time you are wanting to express, but let us suppose, for example, the unit was years. You would write this as 15/12 of a year. You could then simplify this to 5/4 of a year or 1 1/4 years.