[tex]8.(6) = \frac{86 - 8}{9} = \frac{78}{9} = \frac{26}{3} [/tex]
[tex]7.(7) = \frac{77 - 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 = > a) \: 0[/tex]