Answer:
A book is worth $1 and a DVD is worth $12.
Step-by-step explanation:
The equations (2 unknowns and two equations, d is for a DVD and b is for a book):
For David: 3d+4b=40
For Anna: d+6b=18
Now multiply the second equation with -3 and add to the first equation:
 3d+4b=40
 −3d−18b=−54
Combined equation: −14b=−14 and b=1 (means that each book is worth $1).
  
Now for DVD price, use the second equation:
d=18−6 or d=12 (means that each DVD  is worth $12).
A book is worth $1 and a DVD is worth $12.
 
        
             
        
        
        
You need to know the length of two sides and the degree of one angle.
        
             
        
        
        
Two composite numbers that have 8 as a factor are 16 and 24.
        
             
        
        
        
Slope intercept form is y=MX+b.
M is the slope, x is the x intercept, and b is the y intercept
the slope is 

An intercept is where the formula crosses the axis. therefore, the x intercept is .5, and the y intercept is 1
so the point slope formula is 
 
 
        
        
        
Motorcyclist: 2 hours
Bus: 2.5 hours
Truck: 3 hours
Bicyclist: 7.5 hours