What will the distance at which an object should be placed before the convex lens of focal length 12 cm yo obtain a real image of double its size?

The object should be placed at a distance of 18 cm from the convex lens to obtain a real image of double its size. This can be calculated using the lens formula: 1/f = 1/v - 1/u, where f is the focal length of the lens, v is the image distance, and u is the object distance.