Assuming that you mean "fifths", the answer is three fifths.
eight-tenths
It is 31/20 or 1.55
three thirds, four fourths
The answer is: 3/5 plus 2/3 = 19/15
Assuming that you mean "fifths", the answer is three fifths.
120
It is 0.12
11.6
slaves only counted as three-fiths of a vote
eight-tenths
7/10
3/5 = 0.6
It is 31/20 or 1.55
three thirds, four fourths
There is no such word as "fiths".
Assuming that one fiths is your strange way of writing one fifths, the answer is nineteen twentieths.