For diagrams, see your book for ray diagrams for image formation in convex lens.
1. Virtual, erect, magnified image will be formed when object is placed between focus and optical centre.
2. Real and inverted image will be formed when the object is placed beyond focus.(between focus and infinity)
u = -20 cm
f = -10 cm
v = ?
So a virtual and erect image will be formed at
cm from lens or
cm in front of the lens.