Focal length of convex mirror $M_1$ is 20$cm$ and that of concave mirror $M_2$ is 30$cm$. Find position of second image $I_2$. Take first reflection from $M_1$.

For $M_1$,

   $$\begin{gathered} u_1=-20cm \\ {f}_1=+20cm \end{gathered}$$

Using the mirror formula, $\frac{1}{v}+\frac{1}{u}=\frac{1}{f}$, we have

$\frac{1}{v_1}+\frac{1}{-20}=\frac{1}{+20}$

Solving, we get $v_1=+10cm$

For $M_2$,

   $$\begin{gathered} u_2=-40cm (P{I}_1=40cm) \\ {f}_2=-30cm \end{gathered}$$

Using the mirror formula, $\frac{1}{v}+\frac{1}{u}=\frac{1}{f}$, we have

$$\begin{gathered} \frac{1}{v_2}+\frac{1}{-40}=\frac{1}{-30} \\ \therefore v_2=P_2{I}_2=-120cm \end{gathered}$$