Explicație pas cu pas:
[tex]abc + bac = 1666\\ 100a + 10b + c + 100b + 10a + c = 1666 \\ 110a+110b+2c=1666 \\ 110(a + b) = 1666 - 2c[/tex]
[tex]1 \leqslant a \leqslant 9 \\ 1 \leqslant b \leqslant 9 \\c = 3 \: sau \: c = 8[/tex]
c = 3:
[tex]110(a + b) = 1666 - 6 = 1660 \\ 11(a + b) = 166 \: fara \: solutie[/tex]
c = 8:
[tex]110(a + b) = 1666 - 16 = 1650 \\ a + b = 15[/tex]
a = 6 => b = 9 => 698
a = 7 => b = 8 => 788
a = 8 => b = 7 => 878
a = 9 => b = 6 => 968