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?

112

288

360

432

Answer 1

since x=0.8x+72 you can simplify that equation into
x-0.8x=72 -> 0.2x=72 -> x=72/0.2 -> x= 360
that means 360 people became members of the site this month in total.
but it said 80% of total people were between 30 and 40 years old
so
take 80% of 360
360*0.8=288

so the answer is 288

Answer 2

thanks