i'm very clueless and i really need to know what the surface area of a triangular prism (i’m taking the formula quiz by the way)

Use the elimination method to find the solution to the system of equations. 2x - 3y = -9 -x + 3y = 6

The center of the circumscribed circle lies on line segment and the longest side of the triangle is equal to the of the circle.

Solve 3x-18=2y and 5x-6y=6 by elimination show work