Which of the following in not an essential part of a two-column proof?

You are a clerk at convenience store. a customer owes 11.69 for a bag of potatoes chips. she gives you a five dollar bill. how much change should the customer receive?

Jenisey has $24 to spend on seven pencils. after buying them she had $10. how much did each pencil cost.?

What is the 17th term in the arithmetic sequence in which a6 is 101 and a9 is 83