If one side of a triangle is 15 and another side is 20, then the third side 
can be any length between 5 and 35. There are an infinite number of 
possible triangles.
IF it happens to be a RIGHT triangle AND side 'a' and side 'b' happen 
to be its legs, then the length of the third side is 25.  But you didn't 
mention any of those details.  
        
             
        
        
        
X + Y = 50
X = Y + 6
X = 28
Y = 22
28 + 22 = 50
28 - 22 = 6 (28= 22 + 6)
There are 28 students in the larger class.
Hope this helps :)
        
             
        
        
        
Step-by-step explanation:
Answer: 3x-7
Explanation: x times 3 
(3x)
subtracted by 7
(3x-7)
Is this what you are looking for?
 
        
             
        
        
        
Angles in a triangle adds up to 180 
180 - (25.5 +120.2) = 34.3
So, missing angle is 34.3 degrees
Hope this helps!