Alocal garden club had 14 members with a mean age of 34. then two new members joined. one was 24 years old, and the other was 36 years old. how did the mean age change after they joined?

Without knowing the ages of all the different members of the club, I believe that the mean would go down due to 24 being an outlier. You generally take the mean by adding up all the numbers and dividing by all the # of given values. Outliers such as 24 would skew the results leaning none way or the other, in this case making it lower than the previous mean.

if you are saying purchasing 3 social media ads and one newspaper ad counts as one purchase then there are:

6 purchases

if you are asking how many of each then:

18 social media ads

6 newspaper ads