Please help explain these to me! The perimeter of a poster board is 302 centimeters. The length is 45 centimeters longer than the width. Find the length and width of the poster board.

The total cost Kirsten paid for registration and classes at the digital academy was $2584. Registration cost $704 and each class was $376. How many classes did she take?

Four people decide to equally share the cost of starting a small business. If they let a fifth person join this endeavor, the cost for each one would be reduced by $20,000. What is the total cost of starting this business?