To find the percentage decrease, we need to find the actual decrease in price, and then, how much it represents from the original price(on this case, yesterday's price).
The actual decrease is the difference between the prices, and it is given by
Now, to find how much it represents(in decimals) of the original price, we divide this decrease by yesterday's price.
And finally, to rewrite this value as a percentage, we multiply it by 100.
There was a 0.9% decrease on the price.