Can you tell us what the expression is in the question?
Answer:
, ![5\ mph](https://tex.z-dn.net/?f=5%5C%20mph)
Step-by-step explanation:
Given
A motorboat takes 5 hours to travel 200 miles upstream and 4 hours to go downstream
Suppose the speed of motorboat in still water and rate of current be x and y respectively.
during upstream
![\Rightarrow 5=\dfrac{200}{x-y}\\\\\Rightarrow x-y=40\quad \ldots(i)](https://tex.z-dn.net/?f=%5CRightarrow%205%3D%5Cdfrac%7B200%7D%7Bx-y%7D%5C%5C%5C%5C%5CRightarrow%20x-y%3D40%5Cquad%20%5Cldots%28i%29)
During downstream
![\Rightarrow 4=\dfrac{200}{x+y}\\\\\Rightarrow x+y=50\quad \ldots(ii)](https://tex.z-dn.net/?f=%5CRightarrow%204%3D%5Cdfrac%7B200%7D%7Bx%2By%7D%5C%5C%5C%5C%5CRightarrow%20x%2By%3D50%5Cquad%20%5Cldots%28ii%29)
Add (i) and (ii) we get
![\Rightarrow 2x=90\\\Rightarrow x=45\ mph](https://tex.z-dn.net/?f=%5CRightarrow%202x%3D90%5C%5C%5CRightarrow%20x%3D45%5C%20mph)
![\therefore y=5\ mph](https://tex.z-dn.net/?f=%5Ctherefore%20y%3D5%5C%20mph)
Thus, the speed of boat in still water is
and rate of current is ![5\ mph](https://tex.z-dn.net/?f=5%5C%20mph)
Answer:
f(x)/3 = -x +7
Step-by-step explanation:
f(x)=-3x+21
To find f(x)/3 divide each side by 3
f(x)/3=-3x/3+21/3
f(x)/3 = -x +7