A 2.26 cm tall object is placed in 18.6 cm in front of a convex lens. The focal length
is 35.8 cm. How far is the image from the lens?

the image is -38.7 cm from the lens

Explanation:

We use the lens equation which says  

where is the distance to the object, is the distance to the image, and  is the focal length.

Now, in our case

,

,

;

therefore,

where the negative sign indicates that the image is virtual and on the same side of the lens as the object.