How far from a convex lens of focal length 20 cm would you place an object to get a virtual image, which is magnified 3 times ?

How far from a convex lens of focal length 20 cm would you place an object to get a real image enlarged three times ?

An object is placed at a certain distance from a convex lens of focal length 20 cm. Find the distance of the object if the image obtained is. magnified 4 times.

A double convex lens of focal length 15 cm is used as a magnifying glass in order to produce an erect image which is 3 times magnified. What is the distance between the object and the lens ?

A convex lens of focal length 15 cm is placed on a plane mirror. An object is placed at 30 cm from the lens. The image is

A convex lens of focal length 15 cm is placed on a plane mirror. An object is placed at 30 cm from the lens. The image is

How far should an object be placed from a concave mirror of focal length 15 cm so as to get an image magnified two times?