Answer :
[tex]\frac{c}{4d}:\frac{3}{8d}=\frac{c}{4d}\times\frac{8d}{3}=\boxed{\frac{2c}{3}}[/tex]
[tex]\frac{c}{4d}: \frac{3 }{8d}=\frac{c}{4d} \cdot \frac{8d}{3 }= \frac{2c}{3}\\\\d\neq0[/tex]
