Hi Devonte11! In order to find the magnitude of a vector, all you need to do is use the Pythagorean theorem.
Let c be the magnitude of Vector A.
c = √(x²+y²); in this case, your ax = x, while your ay = y
substituting the values to the equation gives:
c = √(81+144)
c = 15.099 or ≈ 15