Three and eight times a number.
Three hundred eight.
Well, honey, you write the number 23.8 as "twenty-three point eight." It's as simple as that. Just say it like you mean it and move on with your fabulous self.
If you mean three and eight tenths then it is 3 and 8/10 as a mixed number
You would write it like this: 308,000,000,000
3n
Seven point four three eight.
3.8
7
125
three tenths is 3/10 eight tenths is 8/10
Twelve and eight hundred seventy-three thousandths.