What we know:

- Probability of mother and father smoking is 0.065

- Probability of mother smoking and father non smoker is 0.145

- Probability of non-smoking mother and smoker father is 0.245

- Probability of non-smoking mother and father is 0.545

- If both parents smoke, the probability of the firstborn having asthma is 0.15

- If the father smokes but the mother doesn't, the probability of the first born having asthma is 0.1

- If the father doesn't smoke but the mother does, the probability of the first born having asthma is 0.12

- If none of the parents smoke, the probability of the first born having asthma is 0.05

Using the law of total probability we get that the probability of the first born having asthma is 0.0789.

We want to know if the firstborn has asmtha, what is the probability that one or both of their parents are smokers.

Thank you very much!