Answer as soon as possible! a 3.0 cm object is 12.0 cm from a convex mirror that has a focal length of 20.0 cm. what is the distance of the image from the mirror? what is the height of the image?

(a) The mirror equation which relates the focal length f, the distance of the object and the distance of the image is 

where for sign convention we take the focal length of a convex mirror as negative : .
Since we know the distance of the object from the mirror, , we can find the distance of the image:

from which 

where the negative sign means the image is virtual (located behind the mirror).

(b) We can find the height of the image through the magnification (M) equation:
where  and  are the height of the image and the object, respectively
.Using we can find :

where the positive sign means the image is upright.