Answer:
A
Step-by-step explanation:
We have the equation:

Take the derivative of both sides with respect to x:
![\frac{d}{dx}[x^2+xy-3y]=\frac{d}{dx}[3]](https://tex.z-dn.net/?f=%5Cfrac%7Bd%7D%7Bdx%7D%5Bx%5E2%2Bxy-3y%5D%3D%5Cfrac%7Bd%7D%7Bdx%7D%5B3%5D)
Implicitly differentiate:

Solve for dy/dx:

Divide:

To find dy/dx at (2, 1), substitute 2 for x and 1 for y. So:

Hence, our answer is A.
Answer:
30 = 2x + 3y
Step-by-step explanation:
x is the number of pens bought and y is the number of notbooks bought you graph this and you get a graph that shows you all the combinations.
M(CE) = 78 + 78*4/26 = 90
685,000,000 would be the right number. Hope this helps!