Answer:
b=9,a=12
Step-by-step explanation:
I solved by substitution:
b = 3/4a  ---> plug this into the other equation
a + b = 21   is now    a + 3/4a = 21
Reduce: 7/4a = 21
a = 12
Now solve for b:
b=3/4a is now b=3/4(12)
b=9
 
        
                    
             
        
        
        
Answer:
84
Step-by-step explanation:
Total students he surveyed: 27
Amount that found it something OTHER than easy: 14 (11 moderate + 3 difficult)
This means that  found it something other than easy
 found it something other than easy
Multiply that by 162 to find the proportion for the larger population:
162 * (14/27), and we get 84. 
 
        
             
        
        
        
Velocity
Formula wise:
1/2 x mass x velocity^2
        
                    
             
        
        
        
26.3 (5 out of 19) and 58.5 (72 out of 123) 
May be wrong, but pretty sure it’s right
        
             
        
        
        
Answer:
-1
Step-by-step explanation:
You have to use simultaneous linear equation as there are 2 equations given
use the subtitution method as what I've shown above
Hope you can understand well
Stay safe!