Both Jared and Nicole are correct. You can solve for either variable and use the equivalent expression to create a one-variable equation. Then you can solve. Jared would have created a one-variable equation that can be used to solve for x, whereas Nicole would have created a one-variable equation that can be used to solve for y.
Reading the situation, I can say that Jared and Nicole are correct because they manipulated the equation right. They can either write the equation as y as a function of x then substitute it to the y in the other equation and solve for x. They can also write the equation as x as a function of y and substitute it to x in the other equation and solve for y. For both solution, they will still obtain the same answers.
