\(\frac{1}{f}=\frac{1}{v}-\frac{1}{u}\)

For convex lens,

\(\frac{1}{30}=\frac{1}{v}+\frac{1}{60} \Rightarrow \frac{1}{60}=\frac{1}{v}\)

Similarly for concave lens

\(\frac{1}{-120}=\frac{1}{v}-\frac{1}{40} \Rightarrow \frac{1}{v}=\frac{1}{60}\)

Virtual object \(10\,\mathrm{cm}\) behind plane mirror. 

Hencereal image \(10\,\mathrm{cm}\) infront of mirror or, \(60\,\mathrm{cm}\) from convex lens