How can a population pyramid tell you about where a country has been and where it is headed?

Population pyramids show the structure of a population by comparing relative numbers of people in different age groups. Population structures differ markedly between Less Economically Developed Countries LEDCs and More Economically Developed Countries MEDCs. Population pyramids are used by demographers as a tool for understanding the make-up of a given population, whether a city, country, region, or the world. A population pyramid does not tell you the actual population in numbers. Rather, it displays percentages and shows what portion of people fall into each cohort.

if triangle abc is congruent to triangle def, their interior angles are congruent, because congruent parts of congruent triangles are congruent (cpctc).

that means ∠d is congruent to ∠a; ∠d is equal to 8x - 2.

interior angles of all triangles add to equal 180 degrees, so you can set the sum of these interior angle values equal to 180 and solve for x.

180 = (8x - 2) + 22 + 72

180 = 8x - 2 + 22 + 72

180 = 8x + 92

88 = 8x

11 = x

x = 11