Nicole charges a flat fee of $3 to babysit, as well as $4 per hour. She earned $15 on Friday night. How many hours did she work?

3 hours

Step-by-step explanation: Subtract the flat fee first. 15-3=12. She earned $12 without the flat fee, so divide that by 4. $12/$4 per hour = 3 hours.

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