Вычисли дроби, выполни сложение и вычитание

а) $\frac{5}{14} + \frac{5}{21} = \frac{5 \cdot 3}{14 \cdot 3} + \frac{5 \cdot 2}{21 \cdot 2} = \frac{15}{42} + \frac{10}{42} = \frac{15+10}{42} = \frac{25}{42}$ **Ответ: $\frac{25}{42}$** б) $\frac{5}{14} - \frac{5}{21} = \frac{5 \cdot 3}{14 \cdot 3} - \frac{5 \cdot 2}{21 \cdot 2} = \frac{15}{42} - \frac{10}{42} = \frac{15-10}{42} = \frac{5}{42}$ **Ответ: $\frac{5}{42}$** в) $\frac{17}{30} + \frac{11}{70} = \frac{17 \cdot 7}{30 \cdot 7} + \frac{11 \cdot 3}{70 \cdot 3} = \frac{119}{210} + \frac{33}{210} = \frac{119+33}{210} = \frac{152}{210} = \frac{76}{105}$ **Ответ: $\frac{76}{105}$** г) $\frac{17}{30} - \frac{11}{70} = \frac{17 \cdot 7}{30 \cdot 7} - \frac{11 \cdot 3}{70 \cdot 3} = \frac{119}{210} - \frac{33}{210} = \frac{119-33}{210} = \frac{86}{210} = \frac{43}{105}$ **Ответ: $\frac{43}{105}$** д) $\frac{9}{22} + \frac{2}{121} = \frac{9 \cdot 11}{22 \cdot 11} + \frac{2 \cdot 2}{121 \cdot 2} = \frac{99}{242} + \frac{4}{242} = \frac{99+4}{242} = \frac{103}{242}$ **Ответ: $\frac{103}{242}$** е) $\frac{9}{22} - \frac{2}{121} = \frac{9 \cdot 11}{22 \cdot 11} - \frac{2 \cdot 2}{121 \cdot 2} = \frac{99}{242} - \frac{4}{242} = \frac{99-4}{242} = \frac{95}{242}$ **Ответ: $\frac{95}{242}$**