Given, a convex mirror,
u = -20 cm ; f = 30cm
By mirror formula, 1/f = 1/v + 1/u,
we get v = +12 cm
Height of object = 3 cm
Let height of image = x
-v/u = x/3
-12/20 = x/3
x = 9/5
Therefore, position of object is 12 cm (behind the mirror)
Nature of object is virtual
Size of object = 9/5 cm
This solution is strictly for practice purposes, do not use it during examinations.