According to an almanac, $80 \%$ of adult smokers started smoking before turning 18 years old (a) If 300 adult smokers are randomly selected, how many would we expect to have started smoking before turning 18 years old? (b) Would it be unusual to observe 255 smokers who started smoking before turning 18 years old in a random sample of 300 adult smokers? Why? (a) We would expect about adult smokers to have started smoking before turning 18 years old. (Type a whole number.)

Step 1 ：Given that 80% of adult smokers started smoking before they turned 18, we can calculate the expected number of adult smokers who started smoking before turning 18 in a sample of 300 adult smokers.

Step 2 ：Let's denote the total number of smokers as \(total\_smokers = 300\) and the percentage of smokers who started before 18 as \(percentage\_started\_before\_18 = 0.8\).

Step 3 ：We can calculate the expected number of smokers who started before 18 by multiplying the total number of smokers by the percentage of smokers who started before 18. This gives us \(expected\_smokers\_started\_before\_18 = total\_smokers \times percentage\_started\_before\_18 = 240.0\).

Step 4 ：Final Answer: We would expect about \(\boxed{240}\) adult smokers to have started smoking before turning 18 years old.