Answer: Hello there!
The stock that bought last year had a price of $126, and since then it has gone down by 13%.
You want to know how much is the stock worth now.
If the value has gone down by 13%, then you need to subtract 13% of the value to $126, this is:
the 13% of $126 is equal to: 0.13*$126 = $16.38
then the value now is $126 - $16.38 = $109.62
Another way to think it is:
$126 is 100%, then if the total worth has gone down by 13%, you now have a (100% - 13%) = 87%
now you want to calculate the 87% of $126; this is:
0.87*$126 = $109.62