I understand that this should be a simple algebra-substitution question but have spent several pages trying to arrive at a solution without success. The first picture is of the question. The second is a picture of my latest attempt. I am not sure how it is possible to find the Ki necessary. Some other necessary equations are included in the second image.

\fSuppose the antibiotics binds to the ribosome with a dissociation constant K and reduces the translation rate from 70 to '70 721+[D]/K where [D] is the drug concentration. Show that the growth rate depends on drug concentration as A0 = 1 + [DI/K: and nd IC50, K1, in terms of the dissociation constant K and the ratio of the drugfree growth rate A0 and the maximum drugfree growth rate Am\". A