Răspuns:
Explicație pas cu pas:
- abc+bca+cab= 111(a+b+c)=777
a+b+c=7
dar
- a max 5 pt ca b min= c min=1
a=5...b+c=2+1+1...1 varianta
a=4....b+c=3=1+2=2+1....2 variante
a=3...b+c=4=1+3=2+2=3+1...3 variante
a=2, b+c=5=4+1=3+2=2+3=1+4....4 variante
a=1, b+c=6=1+5=2+4=3+3=4+2=1+5....5 variante
- total 1+2+...+5=5*6/2=15 numere
