[tex]\displaystyle -(8,75-6\frac{4}{9})-(0,25-3\frac{5}{9})=-(\frac{35}{4}-\frac{58}{9})-(\frac{1}{4}-\frac{32}{9})=-\frac{83}{36}-(-\frac{119}{36})=\\\\-\frac{83}{36}+\frac{119}{36}=1[/tex]