The original price is $1200.
The first step is to increase it by 50%. This can be done as:
[tex]\begin{gathered} 1200\cdot(1+0.5) \\ 1200\cdot1.5 \\ 1800 \end{gathered}[/tex]NOTE: to do math with percentages it is better to convert them to decimals. For example, 50% is equal to 0.5 in decimal form. You can convert from percentage to decimal by dividing the percentage by 100.
Then, we reduce this price by 25% (or -0.25):
[tex]\begin{gathered} 1800\cdot(1-0.25) \\ 1800\cdot0.75 \\ 1350 \end{gathered}[/tex]Answer: the final price is $1350.