Help please it’s timed and I’m not sure the answer

One-third of the people from country a claim that they are from country b, and the rest admit they are from country a. one-fourth of the people from country claim that they are from country a, and the rest admit they are from country b. in a combined census of the two countries, one-half of the total claimed to be from a. what is the ratio of the populations of country a to that of country b.

Given: ac and db are diameters. m∠3=

Consider the proof. given: segment ab is parallel to line de. prove: what is the missing statement in step 5?