Your friend asks you to help him with his snow shoveling business and will pay you 3 pennies for the first job. You agree to help if he triples your payment for each job completed. After 2 shoveling jobs, you will receive 9 pennies, and after 3 shoveling jobs, you will receive 27 pennies. Complete and solve the equation that finds the number of pennies he will pay you after the seventh shoveling job.