Luis y teresa tienen 7500 pesos ahorrados el triple de lo que tiene luisa menos de lo que tiene teresa es 4500 pesos cuanto ahorro cada una

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.

How much dextrose 70% must be mixed with dextrose 5% to prepare 1,000 ml of dextrose 20%?

[10 points, algebra 2-simplifying complex fractions]according to my answer key the restrictions are -1 and 4. but why not positive 1?