А: 2/5 + 1/5 =; 8/17 + 5/17 =; 7/9 + 2/9 =; 9/10 + 2/10 =; 7/17 + 9/17 =.

1. \(\frac{2}{5}+\frac{1}{5}=\frac{3}{5}\)
2. \(\frac{8}{17}+\frac{5}{17}=\frac{13}{17}\)
3. \(\frac{7}{9}+\frac{2}{9}=\frac{9}{9}=1\)
4. \(\frac{9}{10}+\frac{2}{10}=\frac{11}{10}=1\frac{1}{10}\)
5. \(\frac{7}{17}+\frac{9}{17}=\frac{16}{17}\)

Ответ: \(\frac{3}{5};\ \frac{13}{17};\ 1;\ 1\frac{1}{10};\ \frac{16}{17}\).