How do you solve equations with variables on both sides?

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.

Can someone me do math because i am having a breakdown rn because i don’t get it

What effect would doubling all the dimensions of a triangular pyramid have on the volume of the pyramid? explain your reasoning.