The mean of three numbers is 6 the mode of three number is 7 what is the least number

Explanation:

The mode is the most frequent value. We could have all 7s, but then that would indicate the mean is 7 (instead of 6). So we can't have all 7s.

Let's say we had two copies of "7" and then some other number x where x < 7 to ensure that the mean is smaller than the mode.

Add up the three items: x+7+7 = x+14

Divide that sum over 3 to compute the mean: (x+14)/3

This mean is 6, so,

(x+14)/3 = mean

(x+14)/3 = 6

x+14 = 3*6

x+14 = 18

x = 18-14

x = 4

The missing item is 4.

The set {4,7,7} has a mean of 6 and mode of 7.

The smallest item in this set is 4.

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