Решение:

1. a) $$2 - \frac{4}{17} = \frac{2 \cdot 17}{17} - \frac{4}{17} = \frac{34}{17} - \frac{4}{17} = \frac{34-4}{17} = \frac{30}{17} = 1 \frac{13}{17}$$
2. б) $$2 \frac{3}{4} + 1 \frac{2}{3} = 2 + \frac{3}{4} + 1 + \frac{2}{3} = (2 + 1) + (\frac{3}{4} + \frac{2}{3}) = 3 + (\frac{3 \cdot 3}{4 \cdot 3} + \frac{2 \cdot 4}{3 \cdot 4}) = 3 + (\frac{9}{12} + \frac{8}{12}) = 3 + \frac{17}{12} = 3 + 1 \frac{5}{12} = 4 \frac{5}{12}$$
3. в) $$5 + 3 \frac{5}{8} = 5 + 3 + \frac{5}{8} = 8 + \frac{5}{8} = 8 \frac{5}{8}$$