Răspuns:
(10a+b-a)/9+(10b+c-b)/9+(10c+a-c)/9=(100a+10b+c-10a-b)/90+(100b+10c+a-10b-c)/90+(100c+10a+b-10c-a)/90
amplificam fiecare termen din stanga cu 10, deci toti numitorii se vor simplifica
100a+10b-10a+100b+10c-10b+100c+10a-10c=100a+10b+c-10a-b+100b+10c+a-10b-c+100c+10a+b-10c-a
100a+100b+100c=100a+100b+100c
100(a+b+c)=100(a+b+c) |:100
a+b+c=a+b+c