Q. Suppose a study is completed that finds that the number of cockroaches in Chandler decreases by 18% every 12 years. In 2020, there were approximately 3.5 million cockroaches in Chandler.

Question

1.) Determine how long it will take for the number of cockroaches in Chandler to decrease by 50%.

Answer 1

if it drops by 18%, then 82% remains after each 12 years. So you want
0.82^(x/12) = 0.5
x = 12 * log0.5/log0.82 = 41.9 years

Note that the actual population does not matter (unless they ask a question about it)