Ответ:

[tex]1 \frac{3}{4} + 2 \frac{1}{4} - 3 \frac{1}{7} = 3 \frac{4}{4} - 3 \frac{1}{7} = 4 - 3 \frac{1}{7} = 3 \frac{7}{7} - 3 \frac{1}{7} = \frac{6}{7} [/tex]