[tex]42-13\frac{1}{6}=42-13-\frac{1}{6}=29-\frac{1}{6}=28+1-\frac{1}{6}=28+\frac{6}{6}-\frac{1}{6}\\\\=28+\frac{6-1}{6}=28+\frac{5}{6}=28\frac{5}{6}\\\\==========================\\\\short:\\\\42-13\frac{1}{6}=41\frac{6}{6}-13\frac{1}{6}=28\frac{5}{6}[/tex]