The last time tia bought pet food, she purchased 25 pounds. this time she needed 38 pounds. what is the percent increase in the amount of food she needed?

So what you're going to do is subtract 38-25 
38-25 is 13
Now we need to divide 13/25 because 25 was the original number.
13/25 is 0.52
Now we need to multiply that by 100%
Then you get 52%
52% is the increase