19 21+21=?

$$\frac{19}{21} + \frac{9}{21} = \frac{19+9}{21} = \frac{28}{21} = \frac{7 \cdot 4}{7 \cdot 3} = \frac{4}{3} = \frac{3+1}{3} = \frac{3}{3} + \frac{1}{3} = 1 \frac{1}{3}$$

Ответ: $$1 \frac{1}{3}$$