Originally, the stock was worth $55, this can be described as 100%
The value decreased by 7.2%
100% - 7.2% = 92.8%
Next step is to turn this percentage into a multiplier or a decimal
To do this, we divide by 100
92.8 / 100 = 0.928
Now we have a number that we can multiply 55 by to give us our final value
$55 x 0.928 = $51.04