On the x-y plane.First of all, I would like to know that are these curves on the x-y plane or the x,y,z-plane?
You don't have to. Here it is easier to solve the problem algebraically.As I was confused as to whether you would have to sketch out the curves with finding the answer.
You have to find such expression f(x) that when you substitute x = t - 2 into it, you get 2t + 1. In this case, it is easy because t and x can be expressed through each other. In particular, you can express t through x. When you substitute this expression of x for t in 2t + 1, you get the required f(x). If later you substitute t - 2 for x in this expression, you again get 2t + 1.What I don't understand there is how you're able to find the formula by using the parametric curve?