Let us use the lens formula
\(\frac 1 v -\frac 1u = \frac 1f\)
Given
u = -60 cm
f = 30 cm
v1 = ?
For the first refraction from a convex lens
\(\frac 1{v_1} + \frac 1{60} = \frac 1{30}\)
So we get
v1 = 60 cm
l1 is the first image by the lens
An image will be produced by the plane image at a 20 cm distance to the left of it
For the second refraction from a convex lens
u = -20 cm
v = ?
f = 30 cm
Using the lens formula
\(\frac 1v - \frac 1{-20} =\frac 1{30}\)
v = -60 cm
The final image is virtual and at a distance of 60 - 40 = 20 cm from the plane mirror.
Therefore, the final image would be formed at a distance of 20 cm from the plane mirror; it would be a virtual image.