12) \((\frac{2}{5} + \frac{13}{15}) \cdot 6\)

$$(\frac{2}{5} + \frac{13}{15}) \cdot 6 = (\frac{2 \cdot 3}{5 \cdot 3} + \frac{13}{15}) \cdot 6 = (\frac{6}{15} + \frac{13}{15}) \cdot 6 = \frac{6 + 13}{15} \cdot 6 = \frac{19}{15} \cdot 6 = \frac{19 \cdot 6}{15} = \frac{19 \cdot 2}{5} = \frac{38}{5} = 7,6$$