Answer:
(d) Walt demands 12 boxes of strawberries.
Step-by-step explanation:
 For every 3 box of strawberries, Walt consumes 2 box of cream 
 
=> For every 1 box of strawberry, he will consumer 2/3 box of cream 
 
 
 
Suppose, he consumes X boxes of strawberries, then he must consume (2/3)*X boxes of cream 
 
Cost = 10*X + 10*(2/3)*X = 200 = Income 
 
=> 10X + 20X/3 = 200 
 
=. 30X + 20X = 600 
 
=> 50X = 600 
 
=> X = 12