з) $$(20-19\frac{3}{4})+(17\frac{3}{4}-17)+(2\frac{1}{2}-\frac{17}{24})$$.

Решим пример:

1. $$(20-19\frac{3}{4})+(17\frac{3}{4}-17)+(2\frac{1}{2}-\frac{17}{24})$$
2. $$20-19\frac{3}{4} = 19\frac{4}{4} - 19\frac{3}{4} = \frac{1}{4}$$
3. $$17\frac{3}{4}-17 = \frac{3}{4}$$
4. $$2\frac{1}{2}-\frac{17}{24} = 2\frac{12}{24} - \frac{17}{24} = \frac{24+12}{24} - \frac{17}{24} = \frac{36}{24} - \frac{17}{24} = \frac{19}{24}$$
5. $$\frac{1}{4} + \frac{3}{4} + \frac{19}{24} = \frac{6}{24} + \frac{18}{24} + \frac{19}{24} = \frac{6+18+19}{24} = \frac{43}{24} = 1\frac{19}{24}$$

Ответ: $$1\frac{19}{24}$$