Amagnified, inverted image is located at a distance of 40.0 cm from a bi-convex lens with a focal length of 12.0 cm. the object distance is
17.2 cm
15.9 cm
10.5 cm
9.23 cm
7.05 cm

The object distance is 17.2 cm

As we know, the lens formula is  =  +  

where v = image distance from the lens
u = object distance from the lens
f = focal length of the lens 
Alos, focal length of convex lens is positive.

⇒  =  +

⇒  =  - 

⇒  = 

⇒ = 

⇒ u =  = 17.2 cm

The answer is d) by requesting advice on science internet sites