Subtract the faster speed:
721.6 - 8.4 = 713.2
Divide by 2 trains:
713.2/2 = 356.6
The slower train is going 356.6 miles per hour.
The faster train is going 356.6 + 8.4 = 365 miles per hour.
 
        
             
        
        
        
Whenever you multiply by a negative number. 
Hopefully that helps you a little.
        
             
        
        
        
Answer:
x=2
Step-by-step explanation:
x+(2x)^2=18
 
        
             
        
        
        
Answer:
  none of the above
  f(x) ≈ 197·1.03^x; approximately 3% daily
Step-by-step explanation:
If we let x represent days, then x/7 represents weeks and we can rewrite f(x) as ...
  f(x/7) = 197·1.25^(x/7) = 197·(1.25^(1/7))^x
  f(x) ≈ 197·1.03^x
__
The daily multiplier of 1.03 represents a daily growth rate of
  1.03 -1 = .03 = 3%
_____
These answers are not found among the offered choices:
f(x) = 197·1.03^x
3% daily growth
Step-by-step explanation: