Most of the information's are already given in the question. It is important to understand the language of the problem for solving the problem. Once the language is understood, then solving the problem is easy.
Let us assume the number of black jelly beans = x
Number of yellow jelly beans = y 
Then from the question we can get to a equation.
3x - 7 = y
We also know from the question that
x + y = 225
x + 3x -7 = 225
4x = 225 + 7
4x = 232
x = 232/4
   = 58
So Cassidy has 58 black jelly beans out of the total of 225 jelly beans
        
             
        
        
        
Since 1 Euro is 1.321 in American money you must convert the value to $200
Divide 200 by 1.321
you get
151.40 in Euros 
        
             
        
        
        
Answer:  
83 Tenths  
830 hundreths  
Step-by-step explanation:  
8.30=8.3 Remove the points and they will give you how many tenths or hundreths
(hope this helps can i plz have brainlist :D hehe)
 
        
                    
             
        
        
        
I hate those F***! Rip my guy