Seven minus a negative six equals a positive one
minus three fifths
We can convert into seventy-fifths. 6 and nine seventy-fifths minus twenty-five seventy-fifths equals negative 6 and thirty-four seventy-fifths.
Two and one fifteenth.
Call it 21 fifths minus 13 fifths, ie 8 fifths which is one-and-three-fifths
Two fifths minus one third is 1/15.
One whole minus two fifths is three fifths.