Вычислите 1 1) \(\frac{10}{21}-\frac{1}{21}\) 2) \(\frac{2}{3}-\frac{5}{18}\) 3) \(\frac{1}{2}+\frac{1}{9}\) 4) \(\frac{1}{2}-\frac{5}{23}\)

1) Вычислите

1) $$ \frac{10}{21}-\frac{1}{21}=\frac{10-1}{21}=\frac{9}{21}=\frac{3 \cdot 3}{3 \cdot 7}=\frac{3}{7} $$

2) $$ \frac{2}{3}-\frac{5}{18}=\frac{2 \cdot 6}{3 \cdot 6}-\frac{5}{18}=\frac{12}{18}-\frac{5}{18}=\frac{12-5}{18}=\frac{7}{18} $$

3) $$ \frac{1}{2}+\frac{1}{9}=\frac{1 \cdot 9}{2 \cdot 9}+\frac{1 \cdot 2}{9 \cdot 2}=\frac{9}{18}+\frac{2}{18}=\frac{9+2}{18}=\frac{11}{18} $$

4) $$ \frac{1}{2}-\frac{5}{23}=\frac{1 \cdot 23}{2 \cdot 23}-\frac{5 \cdot 2}{23 \cdot 2}=\frac{23}{46}-\frac{10}{46}=\frac{23-10}{46}=\frac{13}{46} $$

Ответ: 1) \(\frac{3}{7}\); 2) \(\frac{7}{18}\); 3) \(\frac{11}{18}\); 4) \(\frac{13}{46}\)