Subtract original amount from new amount:
84 - 39 = 45
He bought 45 books.
 
        
             
        
        
        
Problem:
 The area of the patio of a relative's house is 20 square meters.
 The width of the patio is 2 meters.
 What is the length of the patio?
 Solution:
 The area is:
 A = (w) * (l)
 Where,
 w: width
 l: long
 Clearing l we have:
 l = A / w
 Substituting values:
 l = 20/2
 l = 10 meters
        
             
        
        
        
Just list the factors of 24. Those are the possible numbers of students that can be in each row. 
1,2,3,4,6,8,12,24 are the possible row sizes.
        
             
        
        
        
Answer:
A shopkeeper marks:
$200 * 1.4 = $280
Step-by-step explanation:
With a discount of 25%:
$280 * 0.75 = $210
 
        
             
        
        
        
Answer:
8
Step-by-step explanation:
<h2>i'm a 12 year old girl and i get it  so you have to think about the local store  would be half witch would be 4 so the answer is 8
</h2>