[tex]8.(6) = 8 \frac{6}{9} = \frac{8 \times 9 + 6}{9} = \frac{72 + 6}{9} = \frac{78}{9} = \frac{26}{3} [/tex]
[tex]7.(7) = 7\frac{7}{9} = \frac{7 \times 9 + 7}{9} = \frac{63 + 7}{9} = \frac{70}{9} [/tex]
[tex]8.(6) - 7.(7) = \frac{26}{3} - \frac{70}{9} = \frac{78}{9} - \frac{70}{9} = \frac{78 - 70}{9} = \frac{8}{9} = 0.(8)[/tex]
[tex][0.(8)] = 0[/tex]
[tex]=>a)\:0[/tex]
