23 13 45 30 -- --

$$\frac{23}{45} + \frac{13}{30} = \frac{23 \cdot 2}{45 \cdot 2} + \frac{13 \cdot 3}{30 \cdot 3} = \frac{46}{90} + \frac{39}{90} = \frac{85}{90} = \frac{17}{18}$$

Ответ: $$\frac{17}{18}$$