Assuming that you mean "fifths", the answer is three fifths.
one fifth
3.4 or three and two fifths
Subtracting one fifth from one gives 1 - 1/5 = 4/5, or four fifths.
One whole minus two fifths is three fifths.
one fifth
10 and 2/5
Call it 21 fifths minus 13 fifths, ie 8 fifths which is one-and-three-fifths
Four fifths.
1 fifth
16/5 - 14/5 = 2/5
Fourteen and four fifths.
1 and 4 fifths.