At what distance from the lens is the object located if its image is at a distance of 1 m from the lens

At what distance from the lens is the object located if its image is at a distance of 1 m from the lens, the focal length of which is 20 cm?

Let’s use the thin lens formula:
1 / F = 1 / f + 1 / d
1/20 = 1/100 + 1 / d
1 / d = 5 / 100-1 / 100 = 4/100
d = 100/4 = 25cm
In this formula: F is the focal length, f is the distance from the optical center to the image, d is the distance from the object to the optical center.