tentukan nilai yg blm diketahui.... tolong dibantu kak. makasih

[tex]a. \: \frac{6}{24} = \frac{5.25}{21} = \frac{7}{28} \\ \\ b. \frac{4}{20} = \frac{5}{25} = \frac{6}{30} \\ \\ c. \frac{6}{27} = \frac{8}{36} = \frac{14}{63} \\ \\ d. \frac{6}{8} = \frac{15}{20} = \frac{24}{12} [/tex]