Answer : Option B

Explanation :

Let John's initial salary = Rs.100

$MF#%\begin{align}
&\text{Then, after decreasing 50%, john's salary = }100 \times \dfrac{\left(100-50\right)}{100} = 100 \times \dfrac{50}{100} = \text{Rs.}50\\\\
&\text{After the increase by 50%, john's salary = }50 \times \dfrac{\left(100+50\right)}{100}= 50 \times \dfrac{150}{100} = \text{Rs.}75
\end{align} $MF#%

$MF#%\begin{align}
&\text{Loss percentage = }\dfrac{25}{100} \times 100 = 25\%
\end{align} $MF#%