E) $$2,4: k = 3,6:1\frac{2}{3}$$

Решим пропорцию:

1. $$2,4: k = 3,6:1\frac{2}{3}$$$$2,4: k = 3,6:\frac{5}{3}$$$$k=\frac{2,4\cdot\frac{5}{3}}{3,6}$$$$k=\frac{2,4\cdot5}{3,6\cdot3}$$$$k=\frac{2,4\cdot5}{3,6\cdot3}$$$$k=\frac{24\cdot5}{36\cdot3}$$$$k=\frac{2\cdot5}{3\cdot3}$$$$k=\frac{10}{9}=1\frac{1}{9}$$

Ответ: k = 10/9