

So, real and inverted image (A'B') will be formed at 30 cm from the lens and it will be of same size as the object. Now, this real image is at a distance 20 cm from the concave mirror. Since, fm = 10 cm, this real image is at the centre of curvature of the mirror. So, the mirror will form an inverted image A'B' at the same place of same size.
Again, due to refraction in the lens the final image will be formed at AB and will be of same size as that of object. (A''B'')