Two objects AandB are placed at 15cmand25cm from the pole in front...

Let's consider the following diagram-

Let's assume that ${v}_{A}, {v}_{B}$ indicates the distances of the images of objects A and B respectively.

Thus, by mirror formula, for object A, it can be written that

$\begin{cases}\dfrac{1}{v} + \dfrac{1}{u} & = & \dfrac{1}{f} \\ \dfrac{1}{{v}_{A}} + \dfrac{1}{- 15} & = & \dfrac{1}{\left(- 20\right)} \\ \dfrac{1}{{v}_{A}} & = & \dfrac{1}{- 20} + \dfrac{1}{15} \\ = & \dfrac{- 3 + 4}{60} \\ {v}_{A} & = & 60cm\end{cases}$

Similarly, for object B, using mirror formula,

$\begin{cases}\dfrac{1}{{v}_{B}} + \dfrac{1}{\left(- 25\right)} & = & \dfrac{1}{\left(- 20\right)} \\ \dfrac{1}{{v}_{B}} & = & \dfrac{- 1}{20} + \dfrac{1}{25} \\ & = & \dfrac{- 5 + 4}{100} \\ & = & \dfrac{- 1}{100} \\ {v}_{B} & = & - 100cm\end{cases}$

Hence, the distance \left(d\right)$between the images can be calculated as follows:</p><p>$\begin{cases}d & = & {v}_{A} + {v}_{B} \\ & = & \left(60 + 100\right)cm \\ & = & 160cm\end{cases}$