3*(abc) = ccc
300a+30b+3c = 100c+10c+c
300a+30b = 108c
100a + 10b = 36c
Looking at RHS, we can see that C would be greater than 3 to make LHS postive
So for C=4 and a=1
100+10b = 144
b = 4.4
So for C=5 and a=1
100+10b = 180
b = 8
so a = 1, b= 8 and c=5
abc- ab - ac - a - b - c = 40 - 8 - 5 - 1 - 8 - 5 = 13