д) 10/51 : 15/68

д) \(\frac{10}{51} : \frac{15}{68} = \frac{10}{51} \cdot \frac{68}{15} = \frac{10 \cdot 68}{51 \cdot 15} = \frac{680}{765} = \frac{8}{9} = \frac{136}{153} = \frac{40}{45} = \frac{2}{3}\)