Is y=-5x linear or nonlinear ?​

Can someone me with these two circle theorem questions asap?

The difference between two numbers is one. three times the larger number minus two times the smaller number is 9. what are the two numbers

When solving this problem: 3025/5.5 = a/90.75 you get 49912.5 which would be the length of one of the sides of a square when the area is only 90.75 inches. is that answer correct, why, and how is it possible?