Tom buys a CD for $12.00. He sells it for $15.00. $15.00 is what percent of his original cost?

If the ratio of sum of the first m and n terms of an ap is m2 : n2 , show that the ratio of its mth and nth terms is (2m − 1) : (2n − 1).

I'm confused on this could anyone me and show me what i need to do to solve it.

The population of a small rural town in the year 2006 was 2,459. the population can be modeled by the function below, where f(x residents and t is the number of years elapsed since 2006. f(t) = 2,459(0.92)