Given, A=−40‌cm and, f=20‌cm
From the lens formula, we have:
‌

1

v

−‌

1

u

‌=‌

1

f

⇒‌

1

v

‌=‌

1

f

+‌

1

u

⇒‌

1

v

‌=‌

1

20

+‌

1

(−40)

⇒‌

1

v

‌=‌

2−1

40

=‌

1

40

‌v‌=40‌cm
The positive sign describes that the image is formed to the right of the lens.

The image I1 is formed behind the mirror and thus acts as a virtual source for the mirror. The convex mirror forms the image I2, whose distance from the mirror is given by:
‌

1

v

+‌

1

v

=‌

1

f

Here: ‌u=25‌cm
‌f=‌

R

2

=10‌cm
‌

1

v

+‌

1

v

‌=‌

1

f

⇒‌‌‌

1

v

‌=‌

1

f

−‌

1

u

⇒‌

1

v

=‌

1

10

−‌

1

25

⇒‌

1

v

=‌

5−2

50

=‌

3

50

⇒v=+16.67‌cm
Hence, the final image is formed at a distance of 16.67‌cm behind the convex mirror.