To write 8.6 in words, you would write "eight point six." In this case, "point" is used to represent the decimal point. It is important to note that the word "and" is not used when writing decimal numbers in words.
It is: 86 = LXXXVI
86 = eighty-six
86% is 86/100. In its simplest form this is 43/50.
86% = 43/50
Eighty-six.
86%
86 as a roman numeral would be: LXXXVI
0.86
86/100
568/86 = 626/43
86,000,000
The way you wrote it is just fine.