<p>An object is placed in front of a concave mirror such that the magnification produced is <math xmlns="http://www.w3.org/1998/Math/MathML"><mo>-</mo><mn>1</mn><mo>/</mo><mn>3</mn></math>. The distance between the object and its image is found to be 30 cm. If the focal length of the mirror is given by x/4 cm, then find the magnitude of the value of x.</p>