Please help with both of you can!

Afudge recipe calls for 1/2 cup of cocoa if only 1/2 of the recipe is made to how much cocoa should you use

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.

2x minus y equals 6, x plus y equals negative 3