Answer:
a : b : c = 9 : 15 : 20
Step-by-step explanation:
Here, b is common to both the ratios. In order to find the combined ratio of a, b and c, it is required to make the b ratio same in the given ratios.
Therefore,
[tex] \frac{a}{b} = \frac{3}{5} = \frac{3 \times 3}{5 \times 3} = \frac{9}{15} \\ \\ \frac{b}{c} = \frac{3}{4} = \frac{3 \times 5}{4 \times 5} = \frac{15}{20} \\ \\ \implies \: a : b : c = 9 : 15 : 20[/tex]
