Pls help me I’ll give if correct :)

If x = 12 and y = 3, what is the value of x - y 2? 81 6 3 18

On a piece of paper graph f(x)=5•(0.4)^x

Jack has a piece of red ribbon that is two times as long as his piece of blue ribbon. he says that he can use two different equation to find out how long his piece of red ribbon is compared to his piece of blue ribbon is. is he correct? explain his reasoning