
I'm not sure what methods you've learned up to this point but one option is to apply separation of variables:

and then integrate from there,

exponentiate to isolate y,

Apply exponent rule,

rename this e^c as some new constant, perhaps A,

This A can only be positive, non-zero, but absorbing the plus/minus fixes that restriction,

Use your initial information to solve for this unknown value A,

solving for A, dividing by the exponential,

So we get a final result of

apply exponent rule again to get a better looking answer, and factor,

Lemme know if too confusing.
Answer:
a)the largest Herfindahl index possible = 200
b)the four firm concentration ratio = 8%
Step-by-step explanation:
a) from the question, it follows that the largest share any dealer can have is 2% and the sum of all dealer shares must equal 100% of the market.
We therefore have a maximum number of firms to be 100%/2% = 50.
Since we now know that the maximum number of firms is 50,thus;
At a maximum concentration share of 2% for all firms, the largest Herfindahl index possible = number of firms x percentage squared for each firm = 50 x (2)² = 200
b) In the same logic above, the four firm concentration ratio = 4 x share of the market = 4 x 2% = 8%
For every 3 tablespoons of cocoa, Nate uses 1 tablespoon of sugar.
Since the sugar is halved, the cocoa should be halved as well. 6/2 is 3.