I tried to create a puzzle in the form :
MEUM+TUUM= a sum
MEUM-TUUM= a difference,
" a sum" and " a difference" represent 4-letter valid English words making my cryptic uniquely solvable.
The best I' 've got was:
1. SOLVE IT. There is only one solution, satisfying BOTH equations.
2. Try to find better (i.e. less archaic) English words for the sum and the difference
of my original quest, leading to a single solution ( not necessarily mine).