Given and c is a real number, what is the multiplicative inverse of 4c + 5?

For the answer to the question on what is the multiplicative inverse of 4c + 5 if the given and c is a real number x = 4c+5?
I think the question is incomplete. Good thing I answered this before.
4c = x-5 

c=0.25*(x-5) 

c^-1 = 1/(0.25*(x-5))

Hello there 

Given and c is a real number, what is the multiplicative inverse of 4c + 5?

1/(0.25*(x-5))