In geotown, there are 210 teenagers that own a tablet. this is at least 4/5 of all teenagers that live in geotown. what is the maximum number of teenagers who live in geotown?

Let x = the number of teenagers in Geotown.

At least 4/5 of x equals 210. Therefore
(4/5)x ≥ 210
Multiply each side by 5.
4x ≥ 210*5 = 1050
x ≥ 1050/4 = 262.5

Because x ≥ 262.5,  therefore x = 263 (x must be an integer).

263