III часть: 1) 11/20 − 5/12; 2) 5/6 − 17/21; 3) 3/16 + 1/24; 4) 5/6 − 22/27; 6) 1/10 + 3/5; б) 5/17 + 2/51; в) 2/19 + 13/57; г) 7/23 + 3/46.

Для сложения и вычитания дробей приводим их к общему знаменателю.

1. \(\frac{11}{20}-\frac{5}{12}=\frac{33}{60}-\frac{25}{60}=\frac{2}{15}\).
2. \(\frac{5}{6}-\frac{17}{21}=\frac{35}{42}-\frac{34}{42}=\frac{1}{42}\).
3. \(\frac{3}{16}+\frac{1}{24}=\frac{9}{48}+\frac{2}{48}=\frac{11}{48}\).
4. \(\frac{5}{6}-\frac{22}{27}=\frac{45}{54}-\frac{44}{54}=\frac{1}{54}\).
5. 6) \(\frac{1}{10}+\frac{3}{5}=\frac{1}{10}+\frac{6}{10}=\frac{7}{10}\).
6. б) \(\frac{5}{17}+\frac{2}{51}=\frac{15}{51}+\frac{2}{51}=\frac{1}{3}\).
7. в) \(\frac{2}{19}+\frac{13}{57}=\frac{6}{57}+\frac{13}{57}=\frac{1}{3}\).
8. г) \(\frac{7}{23}+\frac{3}{46}=\frac{14}{46}+\frac{3}{46}=\frac{17}{46}\).