- \(1\frac{3}{4}+\frac{7}{8}=1\frac{6}{8}+\frac{7}{8}=1\frac{13}{8}=2\frac{5}{8}\).
- \(\frac{1}{12}+\frac{4}{9}=\frac{3}{36}+\frac{16}{36}=\frac{19}{36}\).
- \(\frac{1}{4}+\frac{5}{16}=\frac{4}{16}+\frac{5}{16}=\frac{9}{16}\).
Ответ: \(2\frac{5}{8};\ \frac{19}{36};\ \frac{9}{16}\).