Need help with SQL subqueries

I'm looking for help creating 3 different queries within a health database.

The queries are:

  • List first name and last name for the patients who visited the health facility more than two times.

  • Get the patient numbers and birthdays of patients who are three years older than the youngest patient in all.

  • Get the invoice id, paid status and amount of those unpaid invoices whose amount is greater than the average invoice amount. Also display first name and last name of the patients associated with the invoice.

These are the 4 tables I'm working from and the relationships between them.

I've been struggling to complete these in SQL, hope someone can help! Thanks!

Please post Create table statements for each table with insert statements with sample data, what you've tried and any errors or invalid results and desired output.

sounds like homework. Please provide ddl and sample data as well as what you have tried