A social networking site recorded that 80% of the people who became members of the site one month were between 30 and 40 years old. The equation below represents this information, where x represents the total number of people who became members of the site that month:

x = 0.8x + 72

How many people who became members of the site that month were between 30 and 40 years of age?

Question

A social networking site recorded that 80% of the people who became members of the site one month were between 30 and 40 years old. The equation below represents this information, where x represents the total number of people who became members of the site that month:

x = 0.8x + 72

How many people who became members of the site that month were between 30 and 40 years of age?

Mercury · Answer

it states that x = the total # of people on the site

so first solve the equation for x (subtract 0.8x from both sides. on the left side you'll end up with 0.2x, so from there divide both sides by 0.2)

now, since it says 80% of people are between 30-40 years old, simply multiply the previous result by 80% (or as a decimal, 0.8)