The "median" of a set is just the middle value for an odd number of ordered elements or the average of the middle two values for an even number of ordered elements. In this case you are four elements so it would be the average of the second and third terms...
Isolate one variable in the system of equations. Use substitution to create a one-variable equation. Then, set the quadratic equation equal to zero and find the discriminant. If the discriminant is negative, then there are no real number solutions. If the discriminant is zero, then there is one real number solution. If the discriminant is positive, then there are two real number solutions.
