Answer:
40 hollow blocks
Step-by-step explanation:
12/3= 4 hollow blocks per hour
10x4=40 hollow blocks in 10 hours 
 
        
             
        
        
        
I think it's B but I'm not 100% sure
 
        
             
        
        
        
Answer:
great :) wbu
Step-by-step explanation:
 
        
                    
             
        
        
        
The numbers of new CDs is 30 and the old CDs is 21.
To solve this problem, we have to write a system of equations in which we would know the numbers of each types of CD she bought.
<h3>System of Equations</h3>
This is used to solve a series or complex of word problems in which we can represent in a mathematical statements;
- Let n represents numbers of new CDs
- Let u represents numbers of old CDs
The equations can be represented as

Let's take equation (i)
Making n the subject of formula

we can put equation (iii) into equation (ii)

Let's put the value of u into equation (i)

From the calculations above, the numbers of new CDs is 30 and the old CDs is 21.
Learn more on system of equations here;
brainly.com/question/13729904
 
        
             
        
        
        
Answer:
120 bhoo
Step-by-step explanation: