Answer: The answer is d : c = 5 : 4.
Step-by-step explanation: We are given the following values of c and d :

We are to find d : c.
We know that
a : b means the division of a to b in the simplest form, where the numerator and denominator do not have any common factor.
So, for the given variables c and d, we get

Thus, d : c = 5 : 4.