I hope that 2-1 means 21.
DE + EF = DF
4x + 10 + 21 = 9x - 15
4x + 31 = 9x - 15
31 = 9x - 4x - 15
31 = 5x - 15
46 = 5x
x = 9 1/5 = 9.2
You want 9x - 15
9*9.2 - 15
82.8 - 15
67.8 <<<<< answer. 
If I have given the wrong meaning to 2-1 (which could mean 1) leave another note and I will correct my work. 
        
             
        
        
        
So we're looking at two rectangles, one cut out of the other, so all you do is find the area of the big one, base times height equals area, minus the area of the small one, base times height equals area. So the equation you have to solve for is this, 
Area=(12.6X14)-(3X8.4)
        
                    
             
        
        
        
Answer:
The car gets 30 miles to the gallon.  After the car has traveled 80 miles , 2 2/3 gallons have been consumed.
Step-by-step explanation:bro trust me
 
        
             
        
        
        
Answer:
3.00156378e13
Step-by-step explanation:
If you like my answer than please mark me brainliest thanks
 
        
                    
             
        
        
        
Velocity * time = distance
40 (miles / hour) * t (hours) = 60 (miles)
Take note how the units work. miles/hour * hours = miles. This is an indication that a formula we picked is correct.
Now, looking at our formula (and neglecting units at this point)
40t = 60
t = 60/40
<span>t = 1.5 hours</span>