Ответ:

[tex]1)\displaystyle\frac{5}{6} +\frac{2}{7} =\frac{35}{42} +\frac{12}{42} =\frac{47}{42} =1\frac{5}{42}[/tex]

[tex]2)\displaystyle\frac{11}{25} -\frac{3}{10} =\frac{22}{50} -\frac{15}{50} =\frac{7}{50}[/tex]

[tex]3)\displaystyle\frac{15}{16} -\frac{3}{4} =\frac{15}{16} -\frac{12}{16} =\frac{3}{16}[/tex]