Last week a jacket cost $39.50. this week the price of the jacket decreased by $4.50. what was the percent of the decrease? round to the nearest tenth.

First, let's create an equation for this problem. Let x represent the percent decrease.
=

Next, cross multiply. 
39.50x = 450

Now, all you would need to do is isolate the x. To do this, you would divide both sides of the equal sign by 39.50. 
x = 11.3924050633

Remember to round the answer to the nearest tenth. 
11.3924050633 ≈ 11.40%

The percent decrease is 11.40%. 

I hope this helps!