p of 60 friends meet for lunch. They greet each other by exchanging system. How many systems  are exchange if it's grandma bump with each of the 59 other?

In a popular online role playing game, players can create detailed designs for their character's "costumes," or appearance. Noah sets up a website where players can buy and sell these costumes online. Information about the number of people who visited the website and the number of costumes purchased in a single day is listed below. 12 visitors purchased no costume. 193 visitors purchased exactly one costume. 19 visitors purchased more than one costume. If next week, he is expecting 400 visitors, about how many would you expect to buy exactly one costume? Round your answer to the nearest whole number.

Please look at the screenshot, thanks.

Raquel and her brother Marcus are huge sports fans. Combined they own 15 sports jerseys. Raquel owns double the amount of Marcus's jerseys plus an additional three. Use x to represent Marcus's amount of jerseys and y to represent Raquel's amount of jerseys. Write a system to represent this situation.